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Citation Examples | Books, Articles, Websites & More

Published on April 9, 2021 by Jack Caulfield . Revised on January 17, 2024.

The most common citation styles are APA and MLA . To cite a source in these styles, you need a brief in-text citation and a full reference.

Use the interactive tool to understand how a citation is structured and see examples for common source types .

As well as switching between styles and sources, you can explore how a citation looks when there are multiple authors, different editions, no publication date, and other common scenarios.

If you’re still not sure how to cite your source correctly, dive into our comprehensive articles. For each source type, we provide a range of examples in APA , MLA , and Chicago style .

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APA Citation Style

Citation examples.

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• APA Style References Guidelines from the American Psychological Association
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• Common Reference Examples Handout
• Journal Article
• Magazine Article
• Newspaper Article
• Edited Book Chapter
• Dictionary Entry
• Government Report
• YouTube Video
• Facebook Post
• Webpage on a Website
• Supplemental Reference Examples
• Archival Documents and Collections

Parenthetical citations:  (Grady et al., 2019; Jerrentrup et al., 2018)

Narrative citations:  Grady et al. (2019) and Jerrentrup et al. (2018)

• If a journal article has a DOI, include the DOI in the reference.
• If the journal article does not have a DOI and is from an academic research database, end the reference after the page range (for an explanation of why, see the  database information  page). The reference in this case is the same as for a print journal article.
• Do not include database information in the reference unless the journal article comes from a database that publishes original, proprietary content, such as UpToDate (see an example on the  database information  page).
• If the journal article does not have a DOI but does have a URL that will resolve for readers (e.g., it is from an online journal that is not part of a database), include the URL of the article at the end of the reference.
• If the journal article has an article number instead of a page range, include the article number instead of the page range (as shown in the Jerrentrup et al. example).

Parenthetical citations:  (Rabinowitz, 2019; Sapolsky, 2017)

Narrative citations:  Rabinowitz (2019) and Sapolsky (2017)

• If the book includes a DOI, include the DOI in the reference after the publisher name.
• Do not include the publisher location.
• If the book does not have a DOI and comes from an academic research database, end the book reference after the publisher name. Do not include  database information  in the reference. The reference in this case is the same as for a print book.

Parenthetical citations:  (Schaefer & Shapiro, 2019; Schulman, 2019)

Narrative citations:  Schaefer and Shapiro (2019) and Schulman (2019)

• If a magazine article has a DOI, include the DOI in the reference.
• If the magazine article does not have a DOI and is from an academic research database, end the reference after the page range. Do not include  database information  in the reference. The reference in this case is the same as for a print magazine article.
• If the magazine article does not have a DOI but does have a URL that will resolve for readers (e.g., it is from an online magazine that is not part of a database), include the URL of the article at the end of the reference.
• If the magazine article does not have volume, issue, and/or page numbers (e.g., because it is from an online magazine), omit the missing elements from the reference (as in the Schulman example).

Parenthetical citation:  (Carey, 2019)

Narrative citation:  Carey (2019)

• If the newspaper article is from an academic research database, end the reference after the page range. Do not include  database information  in the reference. The reference in this case is the same as for a print newspaper article.
• If the newspaper article has a URL that will resolve for readers (e.g., it is from an online newspaper), include the URL of the article at the end of the reference.
• If the newspaper article does not have volume, issue, and/or page numbers (e.g., because it is from an online newspaper), omit the missing elements from the reference, as shown in the example.
• If the article is from a news website (e.g., CNN, HuffPost)—one that does not have an associated daily or weekly newspaper—use the format for a  webpage on a website  instead.

Parenthetical citation:  (Aron et al., 2019)

Narrative citation:  Aron et al. (2019)

• If the edited book chapter includes a DOI, include the chapter DOI in the reference after the publisher name.
• If the edited book chapter does not have a DOI and comes from an academic research database, end the edited book chapter reference after the publisher name. Do not include  database information  in the reference. The reference in this case is the same as for a print edited book chapter.
• Do not create references for chapters of authored books. Instead, write a reference for the whole book and cite the chapter in the text if desired (e.g., Kumar, 2017, Chapter 2).

Parenthetical citation:  (Merriam-Webster, n.d.)

Narrative citation:  Merriam-Webster (n.d.)

• Because entries in  Merriam-Webster’s Dictionary  are updated over time and are not archived, include a  retrieval date  in the reference.
• Merriam-Webster is both the author and the publisher, so the name appears in the author element only to avoid repetition.
• To quote a dictionary definition, view the pages on quotations and  how to quote works without page numbers  for guidance. Additionally, here is an example:  Culture  refers to the “customary beliefs, social forms, and material traits of a racial, religious, or social group” (Merriam-Webster, n.d., Definition 1a).

Parenthetical citation:  (National Cancer Institute, 2019)

Narrative citation:  National Cancer Institute (2019)

The specific agency responsible for the report appears as the author. The names of parent agencies not present in the  group author name  appear in the source element as the publisher. This creates concise in-text citations and complete reference list entries.

Parenthetical citation:  (Harvard University, 2019)

Narrative citation:  Harvard University (2019)

• Use the name of the account that uploaded the video as the author.
• If the account did not actually create the work, explain this in the text if it is important for readers to know. However, if that would mean citing a source that appears unauthoritative, you might also look for the author’s YouTube channel, official website, or other social media to see whether the same video is available elsewhere.

Parenthetical citations:  (APA Databases, 2019; Gates, 2019)

Narrative citations:  APA Databases (2019) and Gates (2019)

• Present the name of the individual or group author the same as you would for any other reference. Then provide the Twitter handle (beginning with the @ sign) in square brackets, followed by a period.
• Provide the first 20 words of the tweet as the title. Count a URL, a hashtag, or an emoji as one word each, and include them in the reference if they fall within the first 20 words.
• If the tweet includes an image, a video, a poll, or a thumbnail image with a link, indicate that in brackets after the title: [Image attached], [Video attached], [Thumbnail with link attached].
• The same format used for Twitter is also used for Instagram.  

Parenthetical citation:  (News From Science, 2019)

Narrative citation:  News From Science (2019)

• Provide the first 20 words of the Facebook post as the title. Count a URL or other link, a hashtag, or an emoji as one word each, and include them in the reference if they fall within the first 20 words. 
• If a status update includes images, videos, thumbnail links to outside sources, or content from another Facebook post (such as when sharing a link), indicate that in square brackets.

Parenthetical citations:  (Fagan, 2019; National Institute of Mental Health, 2018; Woodyatt, 2019; World Health Organization, 2018)

Narrative citations:  Fagan (2019), National Institute of Mental Health (2018), Woodyatt (2019), and World Health Organization (2018)

• Provide as specific a  date  as is available on the webpage. This might be a year only; a year and month; or a year, month, and day.
• Italicize the title of a webpage.
• When the author of the webpage and the publisher of the website are the same, omit the publisher name to avoid repetition (as in the World Health Organization example).
• When contents of a page are meant to be updated over time but are not archived, include a  retrieval date  in the reference (as in the Fagan example).
• Use the webpage on a website format for articles from news websites such as CNN and HuffPost (these sites do not have associated daily or weekly newspapers). Use the  newspaper article category  for articles from newspaper websites such as  The New York Times  or  The Washington Post .
• Create a reference to an open educational resources (OER) page only when the materials are available for download directly (i.e., the materials are on the page and/or can be downloaded as PDFs or other files). If you are directed to another website, create a reference to the specific webpage on that website where the materials can be retrieved. Use this format for material in any OER repository, such as OER Commons, OASIS, or MERLOT.
• Do not create a reference or in-text citation for a whole website. To mention a website in general, and not any particular information on that site, provide the name of the website in the text and include the URL in parentheses. For example, you might mention that you used a website to create a survey.

The following supplemental example references are mention in the  Publication Manual:

• retracted journal or magazine article
• edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM)
• edition of the International Statistical Classification of Diseases and Related Health Problems (ICD)
• religious work
• annotated religious work

Archival document and collections are not presented in the  APA Publication Manual, Seventh Edition . This content is available only on the APA Style website .  This guidance has been expanded from the 6th edition.

Archival sources include letters, unpublished manuscripts, limited-circulation brochures and pamphlets, in-house institutional and corporate documents, clippings, and other documents, as well as such nontextual materials as photographs and apparatus, that are in the personal possession of an author, form part of an institutional collection, or are stored in an archive such as the Archives of the History of American Psychology at the University of Akron or the APA Archives. For any documents like these that are available on the open web or via a database (subscription or nonsubscription), follow the reference templates shown in Chapter 10 of the Publication Manual.

The general format for the reference for an archival work includes the author, date, title, and source. The reference examples shown on this page may be modified for collections requiring more or less specific information to locate materials, for different types of collections, or for additional descriptive information (e.g., a translation of a letter). Authors may choose to list correspondence from their own personal collections, but correspondence from other private collections should be listed only with the permission of the collector.

Keep in mind the following principles when creating references to archival documents and collections:

• As with any reference, the purpose is to direct readers to the source, despite the fact that only a single copy of the document may be available and readers may have some difficulty actually seeing a copy.
• Include as much information as is needed to help locate the item with reasonable ease within the repository. For items from collections with detailed finding aids, the name of the collection may be sufficient; for items from collections without finding aids, more information (e.g., call number, box number, file name or number) may be necessary to help locate the item.
• If several letters are cited from the same collection, list the collection as a reference and provide specific identifying information (author, recipient, and date) for each letter in the in-text citations (see Example 3).
• Use square brackets to indicate information that does not appear on the document.
• Use “ca.” (circa) to indicate an estimated date (see Example 5).
• Use italics for titles of archival documents and collections; if the work does not have a title, provide a description in square brackets without italics.
• Separate elements of the source (e.g., the name of a repository, library, university or archive, and the location of the university or archive) with commas. End the source with a period.
• If a publication of limited circulation is available in libraries, the reference may be formatted as usual for published material, without the archival source.
• Note that private letters (vs. those in an archive or repository) are considered personal communications and cited in the text only.

1. Letter from a repository

Frank, L. K. (1935, February 4). [Letter to Robert M. Ogden]. Rockefeller Archive Center (GEB Series 1.3, Box 371, Folder 3877), Tarrytown, NY, United States.

• Parenthetical citation: (Frank, 1935)
• Narrative citation: Frank (1935)
• Because the letter does not have a title, provide a description in square brackets.

2. Letter from a private collection

Zacharius, G. P. (1953, August 15). [Letter to William Rickel (W. Rickel, Trans.)]. Copy in possession of Hendrika Vande Kemp.

• Parenthetical citation: (Zacharius, 1953)
• Narrative citation: Zacharius (1953)
• In this example, Hendrika Vande Kemp is either the author of the paper or the author of the paper has received permission from Hendrika Vande Kemp to cite a letter in Vande Kemp’s private collection in this way. Otherwise, cite a private letter as a  personal communication .

3. Collection of letters from an archive

Allport, G. W. (1930–1967). Correspondence. Gordon W. Allport Papers (HUG 4118.10), Harvard University Archives, Cambridge, MA, United States.

• Parenthetical citation: (Allport, 1930–1967)
• Narrative citation: Allport (1930–1967)

To cite specific letters in the text, provide the author and range of years as shown in the reference list entry, plus details about who wrote the specific letter to whom and when the specific letter was written.

• Parenthetical citation: (Allport, 1930–1967, G. Boring to Allport, December 26, 1937)
• Narrative citation: Allport (1930–1967, Allport to G. Boring, March 1, 1939)
• Use the parenthetical citation format to cite a letter that E. G. Boring wrote to Allport because Allport is the author in the reference. Use either the parenthetical or narrative citation format to cite letters that Allport wrote.

4. Unpublished papers, lectures from an archive or personal collection

Berliner, A. (1959). Notes for a lecture on reminiscences of Wundt and Leipzig. Anna Berliner Memoirs (Box M50), Archives of the History of American Psychology, University of Akron, Akron, OH, United States.

• Parenthetical citation: (Berliner, 1959)
• Narrative citation: Berliner (1959)

5. Archival/historical source for which the author and/or date is known or is reasonably certain but not stated on the document

Allport, A. (presumed). (ca. 1937). Marion Taylor today—by the biographer [Unpublished manuscript]. Marion Taylor Papers, Schlesinger Library, Radcliffe College, Cambridge, MA, United States.

• Parenthetical citation: (Allport, ca. 1937)
• Narrative citation: Allport (ca. 1937)
• Because the author is reasonably certain but not stated on the document, place the word “presumed” in parentheses after the name, followed by a period.
• Because the date is reasonably certain but not stated on the document, the abbreviation “ca.” (which stands for “circa”) appears before the year in parentheses.

6. Archival source with group author

Subcommittee on Mental Hygiene Personnel in School Programs. (1949, November 5–6). Meeting of Subcommittee on Mental Hygiene Personnel in School Programs. David Shakow Papers (M1360), Archives of the History of American Psychology, University of Akron, Akron, OH, United States.

• Parenthetical citation: (Subcommittee on Mental Hygiene Personnel in School Programs, 1949)
• Narrative citation: Subcommittee on Mental Hygiene Personnel in School Programs (1949)

7. Interview recorded and available in an archive

Smith, M. B. (1989, August 12). Interview by C. A. Kiesler [Tape recording]. President’s Oral History Project, American Psychological Association, APA Archives, Washington, DC, United States.

• Parenthetical citation: (Smith, 1989)
• Narrative citation: Smith (1989)
• For interviews and oral histories recorded in an archive, list the interviewee as the author. Include the interviewer’s name in the description.

8. Transcription of a recorded interview, no recording available

Sparkman, C. F. (1973). An oral history with Dr. Colley F. Sparkman/Interviewer: Orley B. Caudill. Mississippi Oral History Program (Vol. 289), University of Southern Mississippi, Hattiesburg, MS, United States.

• Parenthetical citation: (Sparkman, 1973)
• Narrative citation: Sparkman (1973)

9. Newspaper article clipping, historical, in personal collection

Psychoanalysis institute to open. (1948, September 18). [Clipping from an unidentified Dayton, OH, United States, newspaper]. Copy in possession of author.

• Parenthetical citation: (“Psychoanalysis Institute to Open,” 1948)
• Narrative citation: “Psychoanalysis Institute to Open” (1948)
• Use this format only if you are the person who is in possession of the newspaper clipping.

10. Historical publication of limited circulation

Sci-Art Publishers. (1935). Sci-Art publications [Brochure]. Roback Papers (HUGFP 104.50, Box 2, Folder “Miscellaneous Psychological Materials”), Harvard University Archives, Cambridge, MA, United States.

• Parenthetical citation: (Sci-Art Publishers, 1935)
• Narrative citation: Sci-Art Publishers (1935)

11. Archived photographs, no author and no title

[Photographs of Robert M. Yerkes]. (ca. 1917–1954). Robert Mearns Yerkes Papers (Box 137, Folder 2292), Manuscripts and Archives, Yale University Library, New Haven, CT, United States.

• Parenthetical citation: ([Photographs of Robert M. Yerkes], ca. 1917–1954)
• Narrative citation: [Photographs of Robert M. Yerkes] (ca. 1917–1954)
• Because the archived photographs do not have a title, provide a bracketed description instead.
• Because the archived photographs do not have an author, move the bracketed description to the author position of the reference.

12. Microfilm

U.S. Census Bureau. (1880). 1880 U.S. census: Defective, dependent, and delinquent classes schedule: Virginia [Microfilm]. NARA Microfilm Publication T1132 (Rolls 33–34), National Archives and Records Administration, Washington, DC, United States.

• Parenthetical citation: (U.S. Census Bureau, 1880)
• Narrative citation: U.S. Census Bureau (1880)

Read the full APA guidelines on citing ChatGPT 

OpenAI. (2023).  ChatGPT  (Mar 14 version) [Large language model].  https://chat.openai.com/chat

• Parenthetical citation:  (OpenAI, 2023)
• Narrative citation:  OpenAI (2023)

Author:  The author of the model is OpenAI.

Date:  The date is the year of the version you used. Following the template in Section 10.10, you need to include only the year, not the exact date. The version number provides the specific date information a reader might need.

Title:  The name of the model is “ChatGPT,” so that serves as the title and is italicized in your reference, as shown in the template. Although OpenAI labels unique iterations (i.e., ChatGPT-3, ChatGPT-4), they are using “ChatGPT” as the general name of the model, with updates identified with version numbers.

The version number is included after the title in parentheses. The format for the version number in ChatGPT references includes the date because that is how OpenAI is labeling the versions. Different large language models or software might use different version numbering; use the version number in the format the author or publisher provides, which may be a numbering system (e.g., Version 2.0) or other methods.

Bracketed text  is used in references for additional descriptions when they are needed to help a reader understand what’s being cited. References for a number of common sources, such as journal articles and books, do not include bracketed descriptions, but things outside of the typical peer-reviewed system often do. In the case of a reference for ChatGPT, provide the descriptor “Large language model” in square brackets. OpenAI describes ChatGPT-4 as a “large multimodal model,” so that description may be provided instead if you are using ChatGPT-4. Later versions and software or models from other companies may need different descriptions, based on how the publishers describe the model. The goal of the bracketed text is to briefly describe the kind of model to your reader.

Source:  When the publisher name and the author name are the same, do not repeat the publisher name in the source element of the reference, and move directly to the URL. This is the case for ChatGPT. The URL for ChatGPT is  https://chat.openai.com/chat . For other models or products for which you may create a reference, use the URL that links as directly as possible to the source (i.e., the page where you can access the model, not the publisher’s homepage).

What to include and what to exclude

Works included in a reference list.

The reference list provides a reliable way for readers to identify and locate the works cited in a paper. APA Style papers generally include reference lists, not  bibliographies.

In general, each work cited in the text must appear in the reference list, and each work in the reference list must be cited in the text. Check your work carefully before submitting your manuscript or course assignment to ensure no works cited in the text are missing from the reference list and vice versa, with only the following exceptions.

Works Excluded From a Reference List

There are a few kinds of works that are not included in a reference list. Usually a work is not included because readers cannot recover it or because the mention is so broad that readers do not need a reference list entry to understand the use.

Information on works included in a reference list is covered in Sections 2.12 and 8.4 of the  APA Publication Manual, Seventh Edition

*This guidance has been expanded from the 6th edition.*

• Personal communications  such as emails, phone calls, or text messages are cited in the text only, not in the reference list, because readers cannot retrieve personal communications.
• General mentions of whole websites, whole periodicals, and common software and apps in the text do not require in-text citations or reference list entries because the use is broad and the source is familiar.
• The source of an epigraph does not usually appear in the reference list unless the work is a scholarly book or journal. For example, if you open the paper with an inspirational quotation by a famous person, the source of the quotation does not appear in the reference list because the quotation is meant to set the stage for the work, not substantiate a key point.   
• Quotations from research participants in a study you conducted can be presented and discussed in the text but do not need citations or reference list entries. Citations and reference list entries are not necessary because the quotations are part of your original research. They could also compromise participants’ confidentiality, which is an ethical violation.
• References included in a meta-analysis, which are marked with an asterisk in the reference list, may be cited in the text (or not) at the author’s discretion. This exception is relevant only to authors who are conducting a meta-analysis.

DOIs and URLs

The DOI or URL is the final component of a reference list entry. Because so much scholarship is available and/or retrieved online, most reference list entries end with either a DOI or a URL.

• A DOI is a unique alphanumeric string that identifies content and provides a persistent link to its location on the internet. DOIs can be found in database records and the reference lists of published works.
• A URL specifies the location of digital information on the internet and can be found in the address bar of your internet browser. URLs in references should link directly to the cited work when possible.

Follow these guidelines for including DOIs and URLs in references:

• Include a DOI for all works that have a DOI, regardless of whether you used the online version or the print version.
• If a print work does not have a DOI, do not include any DOI or URL in the reference.
• If an online work has both a DOI and a URL, include only the DOI.
• For works without DOIs from websites (not including academic research databases), provide a URL in the reference (as long as the URL will work for readers).
• For works without DOIs from most  academic research databases , do not include a URL or database information in the reference because these works are widely available. The reference should be the same as the reference for a print version of the work.
• For works from databases that publish original, proprietary material available only in that database (such as the UpToDate database) or for works of limited circulation in databases (such as monographs in the ERIC database), include the name of the database or archive and the URL of the work. If the URL requires a login or is session-specific (meaning it will not resolve for readers), provide the URL of the database or archive home page or login page instead of the URL for the work. See the page on including  database information in references  for more information. 
• If the URL is no longer working or no longer provides readers access to the content you intend to cite, follow the guidance for works with  no source .
• Other alphanumeric identifiers such as the International Standard Book Number (ISBN) and the International Standard Serial Number (ISSN) are not included in APA Style references.

Follow these guidelines to format DOIs and URLs:

• Present both DOIs and URLs as hyperlinks (i.e., beginning with “http:” or “https:”).
• Because a hyperlink leads readers directly to the content, it is not necessary to include the words “Retrieved from” or “Accessed from” before a DOI or URL.
• It is acceptable to use either the default display settings for hyperlinks in your word-processing program (e.g., usually blue font, underlined) or plain text that is not underlined.
• Leave links live if the work is to be published or read online.
• Follow the current recommendations of the International DOI Foundation to format DOIs in the reference list, which as of this publication is as follows:

https://doi.org/ xxxxx

• The string “https://doi.org/” is a way of presenting a DOI as a link, and “xxxxx” refers to the DOI number.
• The preferred format of the DOI has changed over time. Although older works use previous formats (e.g., “http:/dx.doi.org/” or “doi:” or “DOI:” before the DOI number), in your reference list, standardize DOIs into the current preferred format for all entries. For example, use  https://doi.org/10.1037/a0040251  in your reference even though that article, published in 2016, presented the number in an older format.
• Copy and paste the DOI or URL from your web browser directly into your reference list to avoid transcription errors. Do not change the capitalization or punctuation of the DOI or URL. Do not add line breaks manually to the hyperlink; it is acceptable if your word-processing program automatically adds a break or moves the hyperlink to its own line.
• Do not add a period after the DOI or URL because this may interfere with link functionality.

When a DOI or URL is long or complex, you may use shortDOIs or shortened URLs if desired.

• Use the  shortDOI service  provided by the International DOI Foundation to create shortDOIs. A work can have only one DOI and only one shortDOI; the shortDOI service will either produce a new shortDOI for a work that has never had one or retrieve an existing shortDOI.
• Some websites provide their own branded shortened URLs, and independent URL shortening services are available as well. Any shortened URL is acceptable in a reference as long as you check the link to ensure that it takes you to the correct location.
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A Quick Guide to Harvard Referencing | Citation Examples

Published on 14 February 2020 by Jack Caulfield . Revised on 15 September 2023.

Referencing is an important part of academic writing. It tells your readers what sources you’ve used and how to find them.

Harvard is the most common referencing style used in UK universities. In Harvard style, the author and year are cited in-text, and full details of the source are given in a reference list .

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Table of contents

Harvard in-text citation, creating a harvard reference list, harvard referencing examples, referencing sources with no author or date, frequently asked questions about harvard referencing.

A Harvard in-text citation appears in brackets beside any quotation or paraphrase of a source. It gives the last name of the author(s) and the year of publication, as well as a page number or range locating the passage referenced, if applicable:

Note that ‘p.’ is used for a single page, ‘pp.’ for multiple pages (e.g. ‘pp. 1–5’).

An in-text citation usually appears immediately after the quotation or paraphrase in question. It may also appear at the end of the relevant sentence, as long as it’s clear what it refers to.

When your sentence already mentions the name of the author, it should not be repeated in the citation:

Sources with multiple authors

When you cite a source with up to three authors, cite all authors’ names. For four or more authors, list only the first name, followed by ‘ et al. ’:

Sources with no page numbers

Some sources, such as websites , often don’t have page numbers. If the source is a short text, you can simply leave out the page number. With longer sources, you can use an alternate locator such as a subheading or paragraph number if you need to specify where to find the quote:

Multiple citations at the same point

When you need multiple citations to appear at the same point in your text – for example, when you refer to several sources with one phrase – you can present them in the same set of brackets, separated by semicolons. List them in order of publication date:

Multiple sources with the same author and date

If you cite multiple sources by the same author which were published in the same year, it’s important to distinguish between them in your citations. To do this, insert an ‘a’ after the year in the first one you reference, a ‘b’ in the second, and so on:

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A bibliography or reference list appears at the end of your text. It lists all your sources in alphabetical order by the author’s last name, giving complete information so that the reader can look them up if necessary.

The reference entry starts with the author’s last name followed by initial(s). Only the first word of the title is capitalised (as well as any proper nouns).

Sources with multiple authors in the reference list

As with in-text citations, up to three authors should be listed; when there are four or more, list only the first author followed by ‘ et al. ’:

Reference list entries vary according to source type, since different information is relevant for different sources. Formats and examples for the most commonly used source types are given below.

• Entire book
• Book chapter
• Translated book
• Edition of a book

Journal articles

• Print journal
• Online-only journal with DOI
• Online-only journal with no DOI
• General web page
• Online article or blog
• Social media post

Sometimes you won’t have all the information you need for a reference. This section covers what to do when a source lacks a publication date or named author.

No publication date

When a source doesn’t have a clear publication date – for example, a constantly updated reference source like Wikipedia or an obscure historical document which can’t be accurately dated – you can replace it with the words ‘no date’:

Note that when you do this with an online source, you should still include an access date, as in the example.

When a source lacks a clearly identified author, there’s often an appropriate corporate source – the organisation responsible for the source – whom you can credit as author instead, as in the Google and Wikipedia examples above.

When that’s not the case, you can just replace it with the title of the source in both the in-text citation and the reference list:

Prevent plagiarism, run a free check.

Harvard referencing uses an author–date system. Sources are cited by the author’s last name and the publication year in brackets. Each Harvard in-text citation corresponds to an entry in the alphabetised reference list at the end of the paper.

Vancouver referencing uses a numerical system. Sources are cited by a number in parentheses or superscript. Each number corresponds to a full reference at the end of the paper.

A Harvard in-text citation should appear in brackets every time you quote, paraphrase, or refer to information from a source.

The citation can appear immediately after the quotation or paraphrase, or at the end of the sentence. If you’re quoting, place the citation outside of the quotation marks but before any other punctuation like a comma or full stop.

In Harvard referencing, up to three author names are included in an in-text citation or reference list entry. When there are four or more authors, include only the first, followed by ‘ et al. ’

Though the terms are sometimes used interchangeably, there is a difference in meaning:

• A reference list only includes sources cited in the text – every entry corresponds to an in-text citation .
• A bibliography also includes other sources which were consulted during the research but not cited.

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the ‘Cite this Scribbr article’ button to automatically add the citation to our free Reference Generator.

Caulfield, J. (2023, September 15). A Quick Guide to Harvard Referencing | Citation Examples. Scribbr. Retrieved 25 March 2024, from https://www.scribbr.co.uk/referencing/harvard-style/

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Citing Sources: Sample Reference List Citations

• Style Links & Samples
• Sample Reference List Citations
• Sample Notes and Bibliography Citations
• Sample Author Date Citations
• Citing Nontraditional Sources in Chicago
• Sample Citations
• Major Changes to the New MLA
• Capitalization and Personal Names in Foreign Languages
• Citing Primary Sources
• Ancient Texts
• Citation Consultations Policy

When formatting a citation in APA style, pay particular attention to italics, punctuation, indentation, and capitalization.

Many more samples of citations presented in the APA style can be found in the Publication Manual of the American Psychological Association . Please consult this book or a librarian for help with unusual resources.

All of the following samples are taken from:

American Psychological Association. (2010). Publication manual of the American Psychological Association (6th ed.). Washington, DC: American Psychological Association.

(In the above sample, the name of the organization is the author. Note that only proper names are capitalized in the title, and the edition number follows the title.)

Book: (This sample from Purdue OWL )

Calfee, R. C., & Valencia, R. R. (1991).  APA guide to preparing manuscripts for journal publication . Washington, DC: American Psychological Association.

Book with an Editor:

Robinson, D. N. (Ed.). (1992). Social discourse and moral judgment . San Diego, CA: Academic Press.

Note: italicize the title of the book and do not capitalize any words in titles except the first word, proper names, and after a colon. Use the author's or editor's initials only for first and middle names.

Chapter from an Edited Volume or Anthology :

Haybron, D. M. (2008). Philosophy and the science of subjective well-being. In M. Eid & R. J. Larsen (Eds.),  The science of subjective well-being  (pp. 17-43). New York, NY: Guilford Press. 

Scholarly Article:

Fuentes, A. (2016). Contemporary evolutionary theory in biological anthropology: Insight into human evolution,  genomics  and challenges to  racialized  pseudo-science.   Revista   Cuicuilco , 23 (65), 293-304. 

Note: Do not set off the title of the article with quotes, italics, underlines, or capital letters (except for the first word, proper names or after a colon). Italicize the title of the journal and capitalize all words in the title of the journal. This sample includes the volume number (23) which is italicized to set it off from the other numbers. The issue number (65) appears in parentheses and is not italicized. You will also notice that there is no space left between the volume number and the first parenthesis for the issue number.

Scholarly Article (with multiple authors):

Calvo, M. G., & Lang, P. J. (2004). Gaze patterns when looking at emotional pictures: Motivationally biased attention. Motivation and Emotion, 28 , 221-243. https://doi.org/10.1023/B:MOEM.0000040153.26156.ed

Note: This sample includes the volume number (28), which is italicized to set it off from the page numbers. There is no issue number in this example because the journal is paginated by volume. Provide the DOI when available for electronic documents. If a DOI is not available for a scholarly article retrieved online, you should supply the URL of the journal's homepage (NOT the URL from the database). Note authors' names, indentations, spare use of capital letters, page numbers, and use of periods and commas.

Popular Article (with two authors):

Kandel, E. R., & Squire, L. R. (2000, November 10). Neuroscience: Breaking down scientific barriers to the study of brain and mind. Science, 290, 1113-1120.

Note: Do not set off the title of the article with quotes, italics, underlines, or capital letters (except for the first word, proper names, or after a colon). Italicize the title of the magazine and capitalize all keywords in the title. Italicize the volume number to set it off from the page numbers.

Newspaper Article:

Scwartz, J. (1993, September 30). Obesity affects economic, social status. The Washington Post , pp. A1, A4.

Note: Do not set off the title of the article with quotes, italics, underlines, or capital letters (except for the first word, proper names or after a colon). Italicize the title of the newspaper and capitalize all keywords in the title of the newspaper.

Webpage Examples:  (These samples from  Purdue OWL )

Author, A. A. & Author B. B. (Date of publication ,  or  n. d. if no date ). Title of page [Format description when necessary]. Retrieved from https://www.someaddress.com/full/url/

Eco, U. (2015). How to write a thesis [PDF file]. (Farina C. M. & Farina F., Trans.) Retrieved from https://www.researchgate.net/...How_to_write_a_thesis/.../Umberto+Eco-How+to+Write+... (Original work published 1977).

If the page's author is not listed, start with the title. If the date of publication is not listed, use the abbreviation (n.d.):

Spotlight Resources. (n.d.). Retrieved from https://owl.purdue.edu/owl/about_the_owl/owl_information/spotlight_resources.html

Only include a date of access when page content is likely to change over time (ex: if you're citing a wiki):

Purdue University Writing Lab [Facebook page]. (n.d.). Retrieved January 22, 2019, from https://www.facebook.com/PurdueUniversityWritingLab/

Nonperiodical Web Document or Report (Examples: government data such as U.S. Census): (This sample from Purdue OWL )

Author, A. A., & Author, B. B. (Date of publication, or n.d. if no date).  Title of document . Retrieved from https://Web address

Angeli, E., Wagner, J., Lawrick, E., Moore, K., Anderson, M., Soderland, L., & Brizee, A. (2010, May 5).  General format.  Retrieved from http://owl.english.purdue.edu/owl/resource/560/01/

Note: Italicize the title of the website but do not capitalize any words except the first, proper names, and the first word following a colon.

For citing company or industry reports from the library's MarketLine database, also see:

https://guides.library.ualberta.ca/apa-citation-style/business

Publication manual of the American Psychological Association 7.07

If map is within a book, cite as In Title of book after [Type of map].

Cite primary contributors in the Author's space followed by their contributing role in parentheses.

Other forms for [Type of map] include:

• [Demographic map]
• [Topographical map]

Use (n.d.) for No date.

Title of map. (Year). [Type of Map]. Publisher Location: Publisher.

Citation Examples:

Plattsburgh, Clinton County: Dannemora, Peru, Keeseville, Champlain, Rouses Point, New York State, 3rd ed.

(1999). [Road map]. Clifton Park, NY: Jimapco.

Topographical Map:

Berlin, N.Y. - Mass. - VT. (1988). [Topographical map]. reston, VA: U.S. Geological Survey.

Online Map:

Follow the map citation guidelines as above, but also include a stable URL where the map is found.

Title of map. (Year). [Type of map]. Retrieved from http://xxx.xx

Manhattan sightseeing map. (2010). [City map]. Retrieved from http://www.ny.com/maps/shopmap.html

MTA Metro-North railroad. (2010). [Railroad map]. Retrieved from http://www.mta.info/mnr/html/mnrmap.htm

MTA New York City subway. (2010). [Subway map]. Retrieved from http://www.mta.info/nyct/maps/submap.htm

Charts and Graphs

Since the APA manual does not give direct information for citing every type of source, including charts or graphs, they instruct you to follow the example that is most like the source you are trying to cite. Be sure to provide enough information so your readers can locate the source on their own. When possible provide author or creator, year of publication, title, and publishing and/or retrieval data. When citing a chart, graph or map it may be best to follow the citation style for the format in which the information is presented.

All captions for charts should follow the guidelines below for captions for figures.

Captions for Figures (Charts, Graphs, and Maps): Publication manual of the American Psychological Association 5.20-5.25

All captions should be labeled as Figure followed by a number. The caption should begin with a descriptive phrase and include a citation to the original source and copyright information at the end.

Figure 1. Relations between trust beliefs and school adjustment at T1 and loneliness changes during development in early childhood. All paths attained significance at p> .05. Adapted from “The Relation Between Trust Beliefs and Loneliness During Early Childhood, Middle Childhood, and Adulthood,” by K. J. Rotenberg, N. Addis, L. R. Betts, A. Corrigan, C. Fox, Z. Hobson, & … and M. J. Boulton, 2010, Personality and social psychology bulletin , 36, p. 1090. Copyright 2010 by the Society for Personality and Social Psychology, Inc.

Documentaries or Feature Films:

David, L., Bender, L., Burns S.Z. (Producers), & Guggenheim, P.D. (Director). (2006). An inconvenient truth [Motion picture]. United States: Paramount Pictures.

Note : If a film is not available in wide distribution, add the following to the citation after the country of origin: (Available from Distributor name, full address and zip code).

Online Resources

More examples and samples of papers written using the APA style can be found at the following websites:

• APA Style.Org The APA Citation Style's official website, as excerpted from the 6th edition.
• Excelsior College OWL APA style guide from Excelsior College's Online Writing Lab.
• Slate Citation Machine Excellent tool for citing sources in MLA and APA style. Simple fill in the form for the type of source you are citing, i.e. a book, journal article, website, etc., and this tool will show you the way to cite the reference. Be careful of your capitalization.
• Cornell University Library Guide to APA Citation Style

Additional Information for Citing Special Sources

• Ohio Wesleyan University - Citing Maps
• Map Citation Guide from the University of North Carolina
• Citation Fox (citation generator)
• Knight Cite from Calvin College (citation generator)
• Last Updated: Feb 15, 2024 12:48 PM
• URL: https://libguides.dickinson.edu/citing

Home / MLA Sample Paper

MLA Sample Paper

Mla sample paper #1.

If you’ve been wondering how to produce a research paper that is strong in both formatting and writing, you’ve come to the right place.

Check out our first sample paper below. It is a helpful and clearly labeled visual aid to refer to. Note that while these sample papers do not include MLA abstracts , you should check with your instructor to see if an abstract should be included.

Visual Sample Paper

The example research paper below is one that was written in college for a course on the Inklings. The Inklings were a group of writers in England before WWII, including C.S. Lewis and J.R.R. Tolkien.

The abbreviated MLA paper below (linked here without annotations) is about J.R.R. Tolkien’s Lord of the Rings and how the author used myth, story, and song to link all of his works together. Tolkien is famous for creating a fantasy universe called Middle-earth, which readers can’t truly understand until they read all of the books about Middle-earth ( The Silmarillian, The Hobbit, and The Lord of the Rings ).

Since we’re here to learn how to format an essay, we’ve pointed out some important things about the paper to help you write a correctly formatted essay.

For starters, the essay is in MLA format. That means it follows the style manual of the Modern Language Association, which tells you how to format the paper itself and every source you cite. You’ll also see notes like how long a paragraph should be, how to use commas properly, and how to correctly punctuate a title. Some of these guidelines are different from those in APA format , so be sure to confirm you are using the correct style in your paper.

Pay special attention to the MLA format works cited. We only used one type of source (books), but both citations are correct according to the 9th edition of MLA, published in 2021. When you’re writing your own paper, you need to make sure you always use the most recent edition of the style manual. You’ll also want to check with your instructor to see if you need to include an MLA annotated bibliography with your paper, which contains additional information summarizing and evaluating each source after the regular citation.

Whether you need MLA, APA citations , or Chicago style notes, look up the latest edition before turning in a paper.

MLA Sample Paper #2

See below for an example paper or click below to download it as a Word Document.

The MLA header should be one inch from the top and left margins. The heading and the entire paper should be double spaced.

Eli YaffarabeProfessor Rapheor

28 August 2018

Privatization of Prisons in Texas

              The privatization of governmental services has increased dramatically in the past decade as local, state, and federal agencies have searched for ways to cut costs while still meeting their mandated responsibility to provide various public services. This privatizing trend has particularly affected the criminal justice system. Since the early 1990s, privatized correctional facilities have increased significantly, nationally and statewide. This policy has far-ranging consequences not only within the criminal justice system, but as an instructive example for government officials when considering the costs and benefits of privatization as a public policy option. By 2001, thirty states, the District of Columbia, and Puerto Rico had privately-operated correctional facilities (Austin and Coventry 4). This movement has incited considerable debate and controversy, mainly because prison privatization calls for giving the private sector direct control over the lives of a captive human population.

Surprisingly, there has been little objective and concrete analysis of the privatization of prisons in the United States. This is probably for two reasons: first, ideological arguments on the matter have pushed out substantive research, and second, because this trend has only recently accelerated in the U.S. and mainly on a state level. However, case studies and statistics at the state level are more accessible. With capacity for over 30,000 prisoners in 43 facilities, the state of Texas has privatized more of its prison system than any state in the nation (McDonald and Patten Jr. iv).

Yaffarabe 2

              Public policy concerning the criminal justice system has become more daunting and important in the last decade. The problems in the system are twofold: an overcrowding prison population, mainly due to “three strikes” legislation and reducing early parole; and the costs of operating prisons with this growing population (Austin and Coventry). According to the most recent U.S. Department of Justice survey, slightly over 2.2 million people were incarcerated in correctional facilities in this country in 2003. In comparison, in 1993, 1.37 million people were imprisoned in this country (Beck and Harrison 1).

At the same time, the growth of privately operated correctional facilities has increased significantly in this country. Private prisons now hold 95,522 inmates in this country, which is 6.5 percent of total prisoners (Beck and Harrison 5). In Texas, 16,570 inmates (10 percent of its prison population) are held in private facilities, about 10,000 more than the next highest state. Furthermore, six states had at least 25 percent of their prison population housed in private prisons, led by New Mexico (44%), Alaska (31%), and Montana (29%). These current statistics show that while state governments have been forced to manage and operate overcrowded and over-capacity prisons at considerable costs, many have turned to the private sector to operate prisons (McDonald and Patten Jr.). According to the General Accounting Office, prison operating costs have grown steadily since 1980, increasing almost 550 percent since 1980 based on inflation-adjusted dollars (Austin and Coventry 1).

Prison privatization started in the early 1980s, ostensibly to ease the burden on taxpayers by offering financial relief to private companies to run state prisons. Thomas Beasley founded Corrections Corporation of America in 1983, “the nation’s leader in the construction and management of private prisons” (Darling). That year, Corrections Corporation of America set up the first privately-operated prison in Tennessee. Since then, the number of private

Yaffarabe 3

correctional facility firms has grown to 14 (Austin and Coventry 3). The privatization of prisons occurs in two ways. First, state government can contract out (or outsource) specific services in a correctional facility to a private company after a bidding process. Second, and more radically, private companies build their own privately-managed prisons and contract with state governments to house their inmates. This latter approach, giving private correctional facility firms wide latitude over inmates, is taken in the Texas criminal justice system. In fact, many of these privately operated facilities “have no relationship at all with the state governments in these states, other than an obligation to pay corporate income taxes” (McDonald and Patten Jr. v).

(Due to its length, the remainder of this sample paper is omitted).

Yaffarabe 4

Works Cited Page

Austin, James, and Garry Coventry. Emerging Issues on Privatized Prisons . Bureau of Justice Assistance, Feb. 2001, www.ncjrs.gov/pdffiles1/bja/181249.pdf.

Beck, Allen J., and Paige Harrison. Prisoners in 2003 . Bureau of Justice Statistics, Nov. 2004, www.bjs.gov/content/pub/pdf/p03.pdf.

McDonald, Douglas, and Carl Patten Jr. Governments’ Management of Private Prisons . Abt Associates, 15 Sept. 2003, www.ncjrs.gov/pdffiles1/nij/grants/203968.pdf.

Darling, Michael. “Pitt News: University of Pittsburgh Shouldn’t Lend Its Name to Prison Privatization.” CorpWatch , 15 Nov. 2004, corpwatch.org/article/pitt-news-univeristy-pittsburgh-shouldnt-lend-its-name-prison-privatization.

MLA Formatting Guide

MLA Formatting

• Annotated Bibliography
• Bibliography
• Block Quotes
• et al Usage
• In-text Citations
• Paraphrasing
• Page Numbers
• Sample Paper
• Works Cited
• MLA 8 Updates
• MLA 9 Updates
• View MLA Guide

Citation Examples

• Book Chapter
• Journal Article
• Magazine Article
• Newspaper Article
• Website (no author)
• View all MLA Examples

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An in-text citation is a short citation that is placed next to the text being cited. The basic element needed for an in-text citation is the author’s name . The publication year is not required in in-text citations. Sometimes, page numbers or line numbers are also included, especially when text is quoted from the source being cited. In-text citations are mentioned in the text in two ways: as a citation in prose or a parenthetical citation.

Citation in prose

Citations in prose are incorporated into the text and act as a part of the sentence. Usually, citations in prose use the author’s full name when cited the first time in the text. Thereafter, only the surname is used. Avoid including the middle initial even if it is present in the works-cited-list entry. An example of the first citation in prose for a source with one author is given below:

Doug Barry explains the status of the UK.

Parenthetical

Parenthetical citations add only the author’s surname at the end of the sentence in parentheses. An example of a parenthetical citation is given below:

The status of the UK is explained (Barry).

Examples of in-text citations

Here are a few examples of in-text citations for works with various numbers and types of authors:

Use both the first name and surname of the author if you are mentioning the author for the first time in the prose. In subsequent occurrences, use only the author’s surname. Always use only the author’s surname in parenthetical citations.

Citation in prose:

First mention: Stephen George asserts …. (17).

Subsequent occurrences: George argues …. (17).

Parenthetical:

…. (George 17).

Two authors

Use the first name and surname of both authors if you are mentioning the work for the first time in the prose. In subsequent occurrences, use only the surnames of the two authors. Always use only the authors’ surnames in parenthetical citations. Use “and” to separate the two authors in parenthetical citations.

First mention: Kane Williams and Clark Ronald ….

Subsequent occurrences: Williams and Ronald ….

…. (Williams and Ronald).

Three or more authors

For citations in prose, use the first name and surname of the first author followed by “and others” or “and colleagues.” For parenthetical citations, use only the surname of the first author followed by “et al.”

Krishnan Sethu and colleagues…. or Krishnan Sethu and others ….

…. (Sethu et al.).

Corporate author

For citations in prose, treat the corporate author like you would treat the author’s name. For parenthetical citations, shorten the organization name to the shortest noun phrase. For example, shorten the Modern Language Association of America to Modern Language Association.

The Language Literary Association of Canada….

…. (Language Literary Association).

If there is no author for the source, use the source’s title in place of the author’s name for both citations in prose and parenthetical citations.

When you add such in-text citations, italicize the text of the title. If the source title is longer than a noun phrase, use a shortened version of the title. For example, shorten the title Fantastic Beasts and Where to Find Them to Fantastic Beasts .

Endgame explains …. (121).

…. ( Endgame 121).

In MLA style, two types of citations are used to cite a source: a short citation used within the text (called the in-text citation) and a full citation (called the works cited list entry) within the works cited list, which appears at the end of a paper.

The works cited list entry provides the complete details of a source. An in-text citation is a short citation that is placed next to the text being cited. The in-text citation lets the reader know that the information is derived from the cited source, and helps the reader find the full citation within the works cited list.

In order to properly cite a source in MLA style, you must have both citation types in your paper. Every in-text citation has a works cited list entry. Every works cited list entry has at least one (maybe more) corresponding in-text citation.

In-text citations

The basic element needed for an in-text citation is the author’s surname . The publication year is not required in in-text citations. Sometimes, page numbers or line numbers are also included, especially when text is quoted from the source being cited.

First mention: Sian Anderson studies ….

Subsequent occurrences: Anderson analyzes ….

….(Anderson)

or if quoting directly:

…(Anderson 9)

First mention: Paul Fin and Anna Gabriel ….

Subsequent occurrences: Fin and Gabriel ….

….(Fin and Gabriel)

…(Fin and Gabriel 27)

Paul Hill and colleagues…. or Paul Hill and others ….

….(Hill et al.)

…(Hill et al. 138)

Examples of works cited list entries

Below are a few examples of different types of works cited list entries. The examples given are for one author.

Steinman, Louise. The Knowing Body: Elements of Contemporary Performance and Dance . Shambhala Publications, 1986.

Journal article                                      

Barad, K. “Nature’s Queer Performativity.” Qui Parle , vol. 19, no. 2, 2011, pp. 121–58.

Webpage of a website

Midgelow, Vida L. “Experiences and Perceptions of the Artistic Doctorate: A Survey Report.” Artistic Doctorates in Europe,  5 Feb. 2018, www.artisticdoctorates.com/2017/12/28/experiences-and-perceptions-of-the-artistic-doctorate-survey-report/ .

YouTube video

“Behind the Scenes Chili’s Baby Back Ribs Spot.” YouTube , uploaded by Alvin Chea, 11 Sept. 2017, www.youtube.com/watch?v=gTDLh7gNRYA .

MLA Citation Examples

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How to Cite a Research Paper in APA

Last Updated: October 19, 2022 Fact Checked

This article was co-authored by wikiHow Staff . Our trained team of editors and researchers validate articles for accuracy and comprehensiveness. wikiHow's Content Management Team carefully monitors the work from our editorial staff to ensure that each article is backed by trusted research and meets our high quality standards. There are 12 references cited in this article, which can be found at the bottom of the page. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 158,601 times. Learn more...

If you’re citing a research article or paper in APA style, you’ll need to use a specific citation format that varies depending on the source. Assess whether your source is an article or report published in an academic journal or book, or whether it is an unpublished research paper, such as a print-only thesis or dissertation. Either way, your in-text citations will need to include information about the author (if available) and the date when your source was published or written.

Sample Citations

Writing an In-Text Citation

• For example, you may write, “Gardener (2008) notes, ‘There are several factors to consider about lobsters’ (p. 199).”

• For example, you may write, “‘There are several factors to consider about lobsters’ (Gardner, 2008, p. 199).” Or, “The paper claims, ‘The fallen angel trope is common in religious and non-religious texts’ (Meek & Hill, 2015, p.13-14).”
• For articles with 3-5 authors, write out the names of all the authors the first time you cite the source. For example: (Hammett, Wooster, Smith, & Charles, 1928). In subsequent citations, write only the first author’s name, followed by et al.: (Hammett et al., 1928).
• If there are 6 or more authors for the paper, include the last name of the first author listed and then write "et al." to indicate that there are more than 5 authors.
• For example, you may write, "'This is a quote' (Minaj et al., 1997, p. 45)."

• For example, you may write, “‘The risk of cervical cancer in women is rising’ (American Cancer Society, 2012, p. 2).”

• For example, you may write, “‘Shakespeare may have been a woman’ (“Radical English Literature,” 2004, p. 45).” Or, “The paper notes, ‘There is a boom in Virgin Mary imagery’ (“Art History in Italy,” 2011, p. 32).”

• For example, you may write, “‘There are several factors to consider about lobsters’ (Gardner, 2008, p. 199).” Or, “The paper claims, ‘The fallen angel trope is common in religious and non-religious texts’ (“Iconography in Italian Frescos,” 2015, p.13-14).”

• For example, you may write, “‘There are several factors to consider about lobsters’ (Gardner, 2008, p. 199).” Or, “The paper claims, ‘The fallen angel trope is common in religious and non-religious texts’ (“Iconography in Italian Frescos,” 2015, p.145-146).”

• For example, you may write, “‘The effects of food deprivation are long-term’ (Mett, 2005, para. 18).”

Creating a Reference List Citation for a Published Source

• Material on websites is also considered “published,” even if it’s not peer-reviewed or associated with a formal publishing company.
• While academic dissertations or theses that are print-only are considered unpublished, these types of documents are considered published if they’re included in an online database (such as ProQuest) or incorporated into an institutional repository.

• For example, you may write, “Gardner, L. M.” Or, “Meek, P. Q., Kendrick, L. H., & Hill, R. W.”
• If there is no author, you can list the name of the organization that published the research paper. For example, you may write, “American Cancer Society” or “The Reading Room.”
• Formally published documents that don’t list an author or that have a corporate author are typically reports or white papers .

• For example, you may write, “Gardner, L. M. (2008).” Or, “American Cancer Society. (2015).”

• For example, you may write, “Gardner, L. M. (2008). Crustaceans: Research and data.” Or, “American Cancer Society. (2015). Cervical cancer rates in women ages 20-45.”

• For example, for a journal article, you may write, “Gardner, L. M. (2008). Crustaceans: Research and data. Modern Journal of Malacostracan Research, 25, 150-305.”
• For a book chapter, you could write: “Wooster, B. W. (1937). A comparative study of modern Dutch cow creamers. In T. E. Travers (Ed.), A Detailed History of Tea Serviceware (pp. 127-155). London: Wimble Press."

• For example, you may write, “Kotb, M. A., Kamal, A. M., Aldossary, N. M., & Bedewi, M. A. (2019). Effect of vitamin D replacement on depression in multiple sclerosis patients. Multiple Sclerosis and Related Disorders, 29, 111-117. Retrieved from PubMed, https://www.ncbi.nlm.nih.gov/pubmed/30708308.
• If you’re citing a paper or article that was published online but did not come from an academic journal or database, provide information about the author (if known), the date of publication (if available), and the website where you found the article. For example: “Hill, M. (n.d.). Egypt in the Ptolemaic Period. Retrieved from https://www.metmuseum.org/toah/hd/ptol/hd_ptol.htm”

Citing Unpublished Sources in Your Reference List

• Print-only dissertations or theses.
• Articles or book chapters that are in press or have been recently prepared or submitted for publication.
• Papers that have been rejected for publication or were never intended for publication (such as student research papers or unpublished conference papers).

• If the paper is currently being prepared for publication, include the author’s name, the year when the current draft was completed, and the title of the article in italics, followed by “Manuscript in preparation.” For example: Wooster, B. W. (1932). What the well-dressed man is wearing. Manuscript in preparation.
• If the paper has been submitted for publication, format the citation the same way as if it were in preparation, but instead follow the title with “Manuscript submitted for publication.” For example: Wooster, B. W. (1932). What the well-dressed man is wearing. Manuscript submitted for publication.
• If the paper has been accepted for publication but is not yet published, replace the date with “in press.” Do not italicize the paper title, but do include the title of the periodical or book in which it will be published and italicize that. For example: Wooster, B. W. (in press). What the well-dressed man is wearing. Milady’s Boudoir.

• If the paper was written for a conference but never published, your citation should look like this: Riker, W. T. (2019, March). Traditional methods for the preparation of spiny lobe-fish. Paper presented at the 325th Annual Intergalactic Culinary Conference, San Francisco, CA.
• For an unpublished paper written by a student for a class, include details about the institution where the paper was written. For example: Crusher, B. H. (2019). A typology of Cardassian skin diseases. Unpublished manuscript, Department of External Medicine, Starfleet Academy, San Francisco, CA.

• For example, you may write, “Pendlebottom, R. H. (2011). Iconography in Italian Frescos (Unpublished doctoral dissertation). New York University, New York, United States.”

Community Q&A

• If you want certain information to stand out in the research paper, then you can consider using a block quote. Thanks Helpful 0 Not Helpful 0

You Might Also Like

• ↑ https://libraryguides.vu.edu.au/apa-referencing/7JournalArticles
• ↑ https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/in_text_citations_author_authors.html
• ↑ https://bowvalleycollege.libguides.com/c.php?g=714519&p=5093747
• ↑ https://guides.libraries.psu.edu/apaquickguide/intext
• ↑ https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/in_text_citations_the_basics.html
• ↑ https://libguides.southernct.edu/c.php?g=7125&p=34582#1951239
• ↑ https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/reference_list_electronic_sources.html
• ↑ https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/reference_list_articles_in_periodicals.html
• ↑ https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/reference_list_books.html
• ↑ https://morlingcollege.libguides.com/apareferencing/unpublished-or-informally-published-work
• ↑ https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/general_apa_faqs.html
• ↑ https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/reference_list_other_print_sources.html

About This Article

To cite a research paper in-text in APA, name the author in the text to introduce the quote and put the publication date for the text in parentheses. At the end of your quote, put the page number in parentheses. If you don’t mention the author in your prose, include them in the citation. Start the citation, which should come at the end of the quote, by listing the author’s last name, the year of publication, and the page number. Make sure to put all of this information in parentheses. If there’s no author, use the name of the organization that published the paper or the first few words from the title. To learn how to cite published and unpublished sources in your reference list, keep reading! Did this summary help you? Yes No

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An APA citation generator is a software tool that will automatically format academic citations in the American Psychological Association (APA) style.

It will usually request vital details about a source -- like the authors, title, and publish date -- and will output these details with the correct punctuation and layout required by the official APA style guide.

Formatted citations created by a generator can be copied into the bibliography of an academic paper as a way to give credit to the sources referenced in the main body of the paper.

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College-level and post-graduate students are most likely to use an APA citation generator, because APA style is the most favored style at these learning levels. Before college, in middle and high school, MLA style is more likely to be used. In other parts of the world styles such as Harvard (UK and Australia) and DIN 1505 (Europe) are used more often.

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In academia, bibliographies are graded on their accuracy against the official APA rulebook, so it is important for students to ensure their citations are formatted correctly. Special attention should also be given to ensure the entire document (including main body) is structured according to the APA guidelines. Our complete APA format guide has everything you need know to make sure you get it right (including examples and diagrams).

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• MyBib will automatically locate all the required information. If any is missing you can add it yourself.
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• Repeat for each citation, then download the formatted list and append it to the end of your paper.

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Daniel is a qualified librarian, former teacher, and citation expert. He has been contributing to MyBib since 2018.

Purdue Online Writing Lab Purdue OWL® College of Liberal Arts

MLA In-Text Citations: The Basics

Welcome to the Purdue OWL

This page is brought to you by the OWL at Purdue University. When printing this page, you must include the entire legal notice.

Copyright ©1995-2018 by The Writing Lab & The OWL at Purdue and Purdue University. All rights reserved. This material may not be published, reproduced, broadcast, rewritten, or redistributed without permission. Use of this site constitutes acceptance of our terms and conditions of fair use.

MLA (Modern Language Association) style is most commonly used to write papers and cite sources within the liberal arts and humanities. This resource, updated to reflect the MLA Handbook (9 th ed.), offers examples for the general format of MLA research papers, in-text citations, endnotes/footnotes, and the Works Cited page.

Guidelines for referring to the works of others in your text using MLA style are covered throughout the  MLA Handbook  and in chapter 7 of the  MLA Style Manual . Both books provide extensive examples, so it's a good idea to consult them if you want to become even more familiar with MLA guidelines or if you have a particular reference question.

Basic in-text citation rules

In MLA Style, referring to the works of others in your text is done using parenthetical citations . This method involves providing relevant source information in parentheses whenever a sentence uses a quotation or paraphrase. Usually, the simplest way to do this is to put all of the source information in parentheses at the end of the sentence (i.e., just before the period). However, as the examples below will illustrate, there are situations where it makes sense to put the parenthetical elsewhere in the sentence, or even to leave information out.

General Guidelines

• The source information required in a parenthetical citation depends (1) upon the source medium (e.g. print, web, DVD) and (2) upon the source’s entry on the Works Cited page.
• Any source information that you provide in-text must correspond to the source information on the Works Cited page. More specifically, whatever signal word or phrase you provide to your readers in the text must be the first thing that appears on the left-hand margin of the corresponding entry on the Works Cited page.

In-text citations: Author-page style

MLA format follows the author-page method of in-text citation. This means that the author's last name and the page number(s) from which the quotation or paraphrase is taken must appear in the text, and a complete reference should appear on your Works Cited page. The author's name may appear either in the sentence itself or in parentheses following the quotation or paraphrase, but the page number(s) should always appear in the parentheses, not in the text of your sentence. For example:

Both citations in the examples above, (263) and (Wordsworth 263), tell readers that the information in the sentence can be located on page 263 of a work by an author named Wordsworth. If readers want more information about this source, they can turn to the Works Cited page, where, under the name of Wordsworth, they would find the following information:

Wordsworth, William. Lyrical Ballads . Oxford UP, 1967.

In-text citations for print sources with known author

For print sources like books, magazines, scholarly journal articles, and newspapers, provide a signal word or phrase (usually the author’s last name) and a page number. If you provide the signal word/phrase in the sentence, you do not need to include it in the parenthetical citation.

These examples must correspond to an entry that begins with Burke, which will be the first thing that appears on the left-hand margin of an entry on the Works Cited page:

Burke, Kenneth. Language as Symbolic Action: Essays on Life, Literature, and Method . University of California Press, 1966.

In-text citations for print sources by a corporate author

When a source has a corporate author, it is acceptable to use the name of the corporation followed by the page number for the in-text citation. You should also use abbreviations (e.g., nat'l for national) where appropriate, so as to avoid interrupting the flow of reading with overly long parenthetical citations.

In-text citations for sources with non-standard labeling systems

If a source uses a labeling or numbering system other than page numbers, such as a script or poetry, precede the citation with said label. When citing a poem, for instance, the parenthetical would begin with the word “line”, and then the line number or range. For example, the examination of William Blake’s poem “The Tyger” would be cited as such:

The speaker makes an ardent call for the exploration of the connection between the violence of nature and the divinity of creation. “In what distant deeps or skies. / Burnt the fire of thine eyes," they ask in reference to the tiger as they attempt to reconcile their intimidation with their relationship to creationism (lines 5-6).

Longer labels, such as chapters (ch.) and scenes (sc.), should be abbreviated.

In-text citations for print sources with no known author

When a source has no known author, use a shortened title of the work instead of an author name, following these guidelines.

Place the title in quotation marks if it's a short work (such as an article) or italicize it if it's a longer work (e.g. plays, books, television shows, entire Web sites) and provide a page number if it is available.

Titles longer than a standard noun phrase should be shortened into a noun phrase by excluding articles. For example, To the Lighthouse would be shortened to Lighthouse .

If the title cannot be easily shortened into a noun phrase, the title should be cut after the first clause, phrase, or punctuation:

In this example, since the reader does not know the author of the article, an abbreviated title appears in the parenthetical citation, and the full title of the article appears first at the left-hand margin of its respective entry on the Works Cited page. Thus, the writer includes the title in quotation marks as the signal phrase in the parenthetical citation in order to lead the reader directly to the source on the Works Cited page. The Works Cited entry appears as follows:

"The Impact of Global Warming in North America." Global Warming: Early Signs . 1999. www.climatehotmap.org/. Accessed 23 Mar. 2009.

If the title of the work begins with a quotation mark, such as a title that refers to another work, that quote or quoted title can be used as the shortened title. The single quotation marks must be included in the parenthetical, rather than the double quotation.

Parenthetical citations and Works Cited pages, used in conjunction, allow readers to know which sources you consulted in writing your essay, so that they can either verify your interpretation of the sources or use them in their own scholarly work.

Author-page citation for classic and literary works with multiple editions

Page numbers are always required, but additional citation information can help literary scholars, who may have a different edition of a classic work, like Marx and Engels's  The Communist Manifesto . In such cases, give the page number of your edition (making sure the edition is listed in your Works Cited page, of course) followed by a semicolon, and then the appropriate abbreviations for volume (vol.), book (bk.), part (pt.), chapter (ch.), section (sec.), or paragraph (par.). For example:

Author-page citation for works in an anthology, periodical, or collection

When you cite a work that appears inside a larger source (for instance, an article in a periodical or an essay in a collection), cite the author of the  internal source (i.e., the article or essay). For example, to cite Albert Einstein's article "A Brief Outline of the Theory of Relativity," which was published in  Nature  in 1921, you might write something like this:

See also our page on documenting periodicals in the Works Cited .

Citing authors with same last names

Sometimes more information is necessary to identify the source from which a quotation is taken. For instance, if two or more authors have the same last name, provide both authors' first initials (or even the authors' full name if different authors share initials) in your citation. For example:

Citing a work by multiple authors

For a source with two authors, list the authors’ last names in the text or in the parenthetical citation:

Corresponding Works Cited entry:

Best, David, and Sharon Marcus. “Surface Reading: An Introduction.” Representations , vol. 108, no. 1, Fall 2009, pp. 1-21. JSTOR, doi:10.1525/rep.2009.108.1.1

For a source with three or more authors, list only the first author’s last name, and replace the additional names with et al.

Franck, Caroline, et al. “Agricultural Subsidies and the American Obesity Epidemic.” American Journal of Preventative Medicine , vol. 45, no. 3, Sept. 2013, pp. 327-333.

Citing multiple works by the same author

If you cite more than one work by an author, include a shortened title for the particular work from which you are quoting to distinguish it from the others. Put short titles of books in italics and short titles of articles in quotation marks.

Citing two articles by the same author :

Citing two books by the same author :

Additionally, if the author's name is not mentioned in the sentence, format your citation with the author's name followed by a comma, followed by a shortened title of the work, and, when appropriate, the page number(s):

Citing multivolume works

If you cite from different volumes of a multivolume work, always include the volume number followed by a colon. Put a space after the colon, then provide the page number(s). (If you only cite from one volume, provide only the page number in parentheses.)

Citing the Bible

In your first parenthetical citation, you want to make clear which Bible you're using (and underline or italicize the title), as each version varies in its translation, followed by book (do not italicize or underline), chapter, and verse. For example:

If future references employ the same edition of the Bible you’re using, list only the book, chapter, and verse in the parenthetical citation:

John of Patmos echoes this passage when describing his vision (Rev. 4.6-8).

Citing indirect sources

Sometimes you may have to use an indirect source. An indirect source is a source cited within another source. For such indirect quotations, use "qtd. in" to indicate the source you actually consulted. For example:

Note that, in most cases, a responsible researcher will attempt to find the original source, rather than citing an indirect source.

Citing transcripts, plays, or screenplays

Sources that take the form of a dialogue involving two or more participants have special guidelines for their quotation and citation. Each line of dialogue should begin with the speaker's name written in all capitals and indented half an inch. A period follows the name (e.g., JAMES.) . After the period, write the dialogue. Each successive line after the first should receive an additional indentation. When another person begins speaking, start a new line with that person's name indented only half an inch. Repeat this pattern each time the speaker changes. You can include stage directions in the quote if they appear in the original source.

Conclude with a parenthetical that explains where to find the excerpt in the source. Usually, the author and title of the source can be given in a signal phrase before quoting the excerpt, so the concluding parenthetical will often just contain location information like page numbers or act/scene indicators.

Here is an example from O'Neill's  The Iceman Cometh.

WILLIE. (Pleadingly) Give me a drink, Rocky. Harry said it was all right. God, I need a drink.

ROCKY. Den grab it. It's right under your nose.

WILLIE. (Avidly) Thanks. (He takes the bottle with both twitching hands and tilts it to his lips and gulps down the whiskey in big swallows.) (1.1)

Citing non-print or sources from the Internet

With more and more scholarly work published on the Internet, you may have to cite sources you found in digital environments. While many sources on the Internet should not be used for scholarly work (reference the OWL's  Evaluating Sources of Information  resource), some Web sources are perfectly acceptable for research. When creating in-text citations for electronic, film, or Internet sources, remember that your citation must reference the source on your Works Cited page.

Sometimes writers are confused with how to craft parenthetical citations for electronic sources because of the absence of page numbers. However, these sorts of entries often do not require a page number in the parenthetical citation. For electronic and Internet sources, follow the following guidelines:

• Include in the text the first item that appears in the Work Cited entry that corresponds to the citation (e.g. author name, article name, website name, film name).
• Do not provide paragraph numbers or page numbers based on your Web browser’s print preview function.
• Unless you must list the Web site name in the signal phrase in order to get the reader to the appropriate entry, do not include URLs in-text. Only provide partial URLs such as when the name of the site includes, for example, a domain name, like  CNN.com  or  Forbes.com,  as opposed to writing out http://www.cnn.com or http://www.forbes.com.

Miscellaneous non-print sources

Two types of non-print sources you may encounter are films and lectures/presentations:

In the two examples above “Herzog” (a film’s director) and “Yates” (a presentor) lead the reader to the first item in each citation’s respective entry on the Works Cited page:

Herzog, Werner, dir. Fitzcarraldo . Perf. Klaus Kinski. Filmverlag der Autoren, 1982.

Yates, Jane. "Invention in Rhetoric and Composition." Gaps Addressed: Future Work in Rhetoric and Composition, CCCC, Palmer House Hilton, 2002. Address.

Electronic sources

Electronic sources may include web pages and online news or magazine articles:

In the first example (an online magazine article), the writer has chosen not to include the author name in-text; however, two entries from the same author appear in the Works Cited. Thus, the writer includes both the author’s last name and the article title in the parenthetical citation in order to lead the reader to the appropriate entry on the Works Cited page (see below).

In the second example (a web page), a parenthetical citation is not necessary because the page does not list an author, and the title of the article, “MLA Formatting and Style Guide,” is used as a signal phrase within the sentence. If the title of the article was not named in the sentence, an abbreviated version would appear in a parenthetical citation at the end of the sentence. Both corresponding Works Cited entries are as follows:

Taylor, Rumsey. "Fitzcarraldo." Slant , 13 Jun. 2003, www.slantmagazine.com/film/review/fitzcarraldo/. Accessed 29 Sep. 2009. 

"MLA Formatting and Style Guide." The Purdue OWL , 2 Aug. 2016, owl.english.purdue.edu/owl/resource/747/01/. Accessed 2 April 2018.

Multiple citations

To cite multiple sources in the same parenthetical reference, separate the citations by a semi-colon:

Time-based media sources

When creating in-text citations for media that has a runtime, such as a movie or podcast, include the range of hours, minutes and seconds you plan to reference. For example: (00:02:15-00:02:35).

When a citation is not needed

Common sense and ethics should determine your need for documenting sources. You do not need to give sources for familiar proverbs, well-known quotations, or common knowledge (For example, it is expected that U.S. citizens know that George Washington was the first President.). Remember that citing sources is a rhetorical task, and, as such, can vary based on your audience. If you’re writing for an expert audience of a scholarly journal, for example, you may need to deal with expectations of what constitutes “common knowledge” that differ from common norms.

Other Sources

The MLA Handbook describes how to cite many different kinds of authors and content creators. However, you may occasionally encounter a source or author category that the handbook does not describe, making the best way to proceed can be unclear.

In these cases, it's typically acceptable to apply the general principles of MLA citation to the new kind of source in a way that's consistent and sensible. A good way to do this is to simply use the standard MLA directions for a type of source that resembles the source you want to cite.

You may also want to investigate whether a third-party organization has provided directions for how to cite this kind of source. For example, Norquest College provides guidelines for citing Indigenous Elders and Knowledge Keepers⁠ —an author category that does not appear in the MLA Handbook . In cases like this, however, it's a good idea to ask your instructor or supervisor whether using third-party citation guidelines might present problems.

There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause.

• While Earth’s climate has changed throughout its history , the current warming is happening at a rate not seen in the past 10,000 years.
• According to the Intergovernmental Panel on Climate Change ( IPCC ), "Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact." 1
• Scientific information taken from natural sources (such as ice cores, rocks, and tree rings) and from modern equipment (like satellites and instruments) all show the signs of a changing climate.
• From global temperature rise to melting ice sheets, the evidence of a warming planet abounds.

The rate of change since the mid-20th century is unprecedented over millennia.

Earth's climate has changed throughout history. Just in the last 800,000 years, there have been eight cycles of ice ages and warmer periods, with the end of the last ice age about 11,700 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.

The current warming trend is different because it is clearly the result of human activities since the mid-1800s, and is proceeding at a rate not seen over many recent millennia. 1 It is undeniable that human activities have produced the atmospheric gases that have trapped more of the Sun’s energy in the Earth system. This extra energy has warmed the atmosphere, ocean, and land, and widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.

Earth-orbiting satellites and new technologies have helped scientists see the big picture, collecting many different types of information about our planet and its climate all over the world. These data, collected over many years, reveal the signs and patterns of a changing climate.

Scientists demonstrated the heat-trapping nature of carbon dioxide and other gases in the mid-19th century. 2 Many of the science instruments NASA uses to study our climate focus on how these gases affect the movement of infrared radiation through the atmosphere. From the measured impacts of increases in these gases, there is no question that increased greenhouse gas levels warm Earth in response.

Scientific evidence for warming of the climate system is unequivocal.

Intergovernmental Panel on Climate Change

Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly 10 times faster than the average rate of warming after an ice age. Carbon dioxide from human activities is increasing about 250 times faster than it did from natural sources after the last Ice Age. 3

The Evidence for Rapid Climate Change Is Compelling:

Global Temperature Is Rising

The planet's average surface temperature has risen about 2 degrees Fahrenheit (1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide emissions into the atmosphere and other human activities. 4 Most of the warming occurred in the past 40 years, with the seven most recent years being the warmest. The years 2016 and 2020 are tied for the warmest year on record. 5 Image credit: Ashwin Kumar, Creative Commons Attribution-Share Alike 2.0 Generic.

The Ocean Is Getting Warmer

The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of ocean showing warming of 0.67 degrees Fahrenheit (0.33 degrees Celsius) since 1969. 6 Earth stores 90% of the extra energy in the ocean. Image credit: Kelsey Roberts/USGS

The Ice Sheets Are Shrinking

The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost an average of 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year. 7 Image: The Antarctic Peninsula, Credit: NASA

Glaciers Are Retreating

Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa. 8 Image: Miles Glacier, Alaska Image credit: NASA

Snow Cover Is Decreasing

Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and the snow is melting earlier. 9 Image credit: NASA/JPL-Caltech

Sea Level Is Rising

Global sea level rose about 8 inches (20 centimeters) in the last century. The rate in the last two decades, however, is nearly double that of the last century and accelerating slightly every year. 10 Image credit: U.S. Army Corps of Engineers Norfolk District

Arctic Sea Ice Is Declining

Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades. 11 Credit: NASA's Scientific Visualization Studio

Extreme Events Are Increasing in Frequency

The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events. 12 Image credit: Régine Fabri,  CC BY-SA 4.0 , via Wikimedia Commons

Ocean Acidification Is Increasing

Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30%. 13 , 14 This increase is due to humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the ocean. The ocean has absorbed between 20% and 30% of total anthropogenic carbon dioxide emissions in recent decades (7.2 to 10.8 billion metric tons per year). 1 5 , 16 Image credit: NOAA

1. IPCC Sixth Assessment Report, WGI, Technical Summary . B.D. Santer et.al., “A search for human influences on the thermal structure of the atmosphere.” Nature 382 (04 July 1996): 39-46. https://doi.org/10.1038/382039a0. Gabriele C. Hegerl et al., “Detecting Greenhouse-Gas-Induced Climate Change with an Optimal Fingerprint Method.” Journal of Climate 9 (October 1996): 2281-2306. https://doi.org/10.1175/1520-0442(1996)009<2281:DGGICC>2.0.CO;2. V. Ramaswamy, et al., “Anthropogenic and Natural Influences in the Evolution of Lower Stratospheric Cooling.” Science 311 (24 February 2006): 1138-1141. https://doi.org/10.1126/science.1122587. B.D. Santer et al., “Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes.” Science 301 (25 July 2003): 479-483. https://doi.org/10.1126/science.1084123. T. Westerhold et al., "An astronomically dated record of Earth’s climate and its predictability over the last 66 million years." Science 369 (11 Sept. 2020): 1383-1387. https://doi.org/10.1126/science.1094123

2. In 1824, Joseph Fourier calculated that an Earth-sized planet, at our distance from the Sun, ought to be much colder. He suggested something in the atmosphere must be acting like an insulating blanket. In 1856, Eunice Foote discovered that blanket, showing that carbon dioxide and water vapor in Earth's atmosphere trap escaping infrared (heat) radiation. In the 1860s, physicist John Tyndall recognized Earth's natural greenhouse effect and suggested that slight changes in the atmospheric composition could bring about climatic variations. In 1896, a seminal paper by Swedish scientist Svante Arrhenius first predicted that changes in atmospheric carbon dioxide levels could substantially alter the surface temperature through the greenhouse effect. In 1938, Guy Callendar connected carbon dioxide increases in Earth’s atmosphere to global warming. In 1941, Milutin Milankovic linked ice ages to Earth’s orbital characteristics. Gilbert Plass formulated the Carbon Dioxide Theory of Climate Change in 1956.

3. IPCC Sixth Assessment Report, WG1, Chapter 2 Vostok ice core data; NOAA Mauna Loa CO2 record O. Gaffney, W. Steffen, "The Anthropocene Equation." The Anthropocene Review 4, issue 1 (April 2017): 53-61. https://doi.org/abs/10.1177/2053019616688022.

4. https://www.ncei.noaa.gov/monitoring https://crudata.uea.ac.uk/cru/data/temperature/ http://data.giss.nasa.gov/gistemp

5. https://www.giss.nasa.gov/research/news/20170118/

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Header image shows clouds imitating mountains as the sun sets after midnight as seen from Denali's backcountry Unit 13 on June 14, 2019. Credit: NPS/Emily Mesner Image credit in list of evidence: Ashwin Kumar, Creative Commons Attribution-Share Alike 2.0 Generic.

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