Wikipedia:Citing sources

A citation, also called a reference,[note 1] uniquely identifies a source of information, e.g.:

Ritter, R. M. (2003). The Oxford Style Manual. Oxford University Press. p. 1. ISBN 978-0-19-860564-5.

Wikipedia's verifiability policy requires inline citations for any material challenged or likely to be challenged, and for all quotations, anywhere in article space.

A citation or reference in an article usually has two parts. In the first part, each section of text that is either based on, or quoted from, an outside source is marked as such with an inline citation. The inline citation may be a superscript footnote number, or an abbreviated version of the citation called a short citation. The second necessary part of the citation or reference is the list of full references, which provides complete, formatted detail about the source, so that anyone reading the article can find it and verify it.

This page explains how to place and format both parts of the citation. Each article should use one citation method or style throughout. If an article already has citations, preserve consistency by using that method or seek consensus on the talk page before changing it (the principle is reviewed at § Variation in citation methods). While you should try to write citations correctly, what matters most is that you provide enough information to identify the source. Others will improve the formatting if needed. See "Help:Referencing for beginners" for a brief introduction on how to put references in Wikipedia articles.

Types of citation

  • A full citation fully identifies a reliable source and, where applicable, the place in that source (such as a page number) where the information in question can be found. For example: Rawls, John. A Theory of Justice. Harvard University Press, 1971, p. 1. This type of citation is usually given as a footnote, and is the most commonly used citation method in Wikipedia articles.
  • An inline citation means any citation added close to the material it supports, for example after the sentence or paragraph, normally in the form of a footnote.
  • A short citation is an inline citation that identifies the place in a source where specific information can be found, but without giving full details of the source – these will have been provided in a full bibliographic citation either in an earlier footnote, or in a separate section. For example: Rawls 1971, p. 1. This system is used in some articles; the short citations may be given either as footnotes, or as parenthetical references within the text.
  • In-text attribution involves adding the source of a statement to the article text, such as Rawls argues that X.[5] This is done whenever a writer or speaker should be credited, such as with quotations, close paraphrasing, or statements of opinion or uncertain fact. The in-text attribution does not give full details of the source – this is done in a footnote in the normal way. See In-text attribution below.
  • A general reference is a citation that supports content, but is not linked to any particular piece of material in the article through an inline citation. General references are usually listed at the end of the article in a References section. They are usually found in underdeveloped articles, especially when all article content is supported by a single source. They may also be listed in more developed articles as a supplement to inline citations.

When and why to cite sources

By citing sources for Wikipedia content, you enable users to verify that the information given is supported by reliable sources, thus improving the credibility of Wikipedia while showing that the content is not original research. You also help users find additional information on the subject; and by giving attribution you avoid plagiarising the source of your words or ideas.

In particular, sources are required for material that is challenged or likely to be challenged – if reliable sources cannot be found for challenged material, it is likely to be removed from the article. Sources are also required when quoting someone, with or without quotation marks, or closely paraphrasing a source. However, the citing of sources is not limited to those situations – editors are always encouraged to add or improve citations for any information contained in an article.

Citations are especially desirable for statements about living persons, particularly when the statements are contentious or potentially defamatory. In accordance with the biography of living persons policy, unsourced information of this type is likely to be removed on sight.

Multimedia

For an image or other media file, details of its origin and copyright status should appear on its file page. Image captions should be referenced as appropriate just like any other part of the article. A citation is not needed for descriptions such as alt text that are verifiable directly from the image itself, or for text that merely identifies a source (e.g., the caption "Belshazzar's Feast (1635)" for File:Rembrandt-Belsazar.jpg).

When not to cite

Citations are not used on disambiguation pages (sourcing for the information given there should be done in the target articles). Citations are often omitted from the lead section of an article, insofar as the lead summarizes information for which sources are given later in the article, although quotations and controversial statements, particularly if about living persons, should be supported by citations even in the lead. See WP:LEADCITE for more information.

What information to include

Listed below is the information that a typical inline citation or general reference will provide, though other details may be added as necessary. This information is included in order to identify the source, assist readers in finding it, and (in the case of inline citations) indicate the place in the source where the information is to be found. (If an article uses parenthetical referencing or short citations, then the inline citations will refer to this information in abbreviated form, as described in the relevant sections above.)

Use details in citing. Good citations are on the left, while citations on the right should be improved.

Examples

Books

Citations for books typically include:

  • name of author(s)
  • title of book
  • volume when appropriate
  • name of publisher
  • place of publication
  • date of publication of the edition
  • chapter or page numbers cited, if appropriate
  • edition, if not the first edition
  • ISBN (optional)

Citations for individually authored chapters in books typically include:

  • name of author(s)
  • title of the chapter
  • name of book's editor
  • name of book and other details as above
  • chapter number or page numbers for the chapter (optional)

In some instances, the verso of a book's title page may record, "Reprinted with corrections XXXX" or similar, where 'XXXX' is a year. This is a different version of a book in the same way that different editions are different versions. In such a case, record: the year of the particular reprint, the edition immediately prior to this particular reprint (if not the first edition) and a note to say "Reprint with corrections". If {{cite}} (or similar) is being used, the notation, "Reprint with corrections", can be added immediately following the template. § Dates and reprints of older publications gives an example of appending a similar textual note.

Journal articles

Citations for journal articles typically include:

  • name of the author(s)
  • year and sometimes month of publication
  • title of the article
  • name of the journal
  • volume number, issue number, and page numbers (article numbers in some electronic journals)
  • DOI and/or other identifiers are optional

Newspaper articles

Citations for newspaper articles typically include:

  • byline (author's name), if any
  • title of the article
  • name of the newspaper in italics
  • city of publication (if not included in name of newspaper)
  • date of publication
  • page number(s) are optional

Web pages

Citations for World Wide Web pages typically include:

  • URL of the specific web page where the referenced content can be found
  • name of the author(s)
  • title of the article
  • title or domain name of the website
  • publisher, if known
  • date of publication
  • page number(s) (if applicable)
  • the date you retrieved (or accessed) the web page (required if the publication date is unknown)

Sound recordings

Citations for sound recordings typically include:

  • name of the composer(s), songwriter(s), script writer(s) or the like
  • name of the performer(s)
  • title of the song or individual track
  • title of the album (if applicable)
  • name of the record label
  • year of release
  • medium (for example: LP, audio cassette, CD, MP3 file)
  • approximate time at which event or point of interest occurs, where appropriate

Do not cite an entire body of work by one performer. Instead, make one citation for each work your text relies on.

Film, television, or video recordings

Citations for films, TV episodes, or video recordings typically include:

  • name of the director
  • name of the producer, if relevant
  • names of major performers
  • the title of a TV episode
  • title of the film or TV series
  • name of the studio
  • year of release
  • medium (for example: film, videocassette, DVD)
  • approximate time at which event or point of interest occurs, where appropriate

Other

Identifying parts of a source

When citing lengthy sources, you should identify which part of a source is being cited.

Books and print articles

Specify the page number or range of page numbers. Page numbers are not required for a reference to the book or article as a whole. When you specify a page number, it is helpful to specify the version (date and edition for books) of the source because the layout, pagination, length, etc. can change between editions.

If there are no page numbers, whether in ebooks or print materials, then you can use other means of identifying the relevant section of a lengthy work, such as the chapter number or the section title.

In some works, such as plays and ancient works, there are standard methods of referring to sections, such as "Act 1, scene 2" for plays and Bekker numbers for Aristotle's works. Use these methods whenever appropriate.

Audio and video sources

Specify the time at which the event or other point of interest occurs. Be as precise as possible about the version of the source that you are citing; for example, movies are often released in different editions or "cuts". Due to variations between formats and playback equipment, precision may not be accurate in some cases. However, many government agencies do not publish minutes and transcripts but do post video of official meetings online; generally the subcontractors who handle audio-visual are quite precise.

Links and ID numbers

A citation ideally includes a link or ID number to help editors locate the source. If you have a URL (web page) link, you can add it to the title part of the citation, so that when you add the citation to Wikipedia the URL becomes hidden and the title becomes clickable. To do this, enclose the URL and the title in square brackets—the URL first, then a space, then the title. For example:

''[http://monographs.iarc.fr/ENG/Monographs/vol66/mono66-7.pdf IARC Monographs On The Evaluation Of Carcinogenic Risks To Humans – Doxefazepam]''. International Agency For Research On Cancer (IARC). 66: 97–104. 13–20 February 1996.

For web-only sources with no publication date, the "Retrieved" date (or the date you accessed the web page) should be included, in case the web page changes in the future. For example: Retrieved 15 July 2011 or you can use the access-date parameter in the automatic Wikipedia:refToolbar 2.0 editing window feature.

You can also add an ID number to the end of a citation. The ID number might be an ISBN for a book, a DOI (digital object identifier) for an article or some e-books, or any of several ID numbers that are specific to particular article databases, such as a PMID number for articles on PubMed. It may be possible to format these so that they are automatically activated and become clickable when added to Wikipedia, for example by typing ISBN (or PMID) followed by a space and the ID number.

If your source is not available online, it should be available in reputable libraries, archives, or collections. If a citation without an external link is challenged as unavailable, any of the following is sufficient to show the material to be reasonably available (though not necessarily reliable): providing an ISBN or OCLC number; linking to an established Wikipedia article about the source (the work, its author, or its publisher); or directly quoting the material on the talk page, briefly and in context.

Linking to pages in PDF files

Links to long PDF documents can be made more convenient by taking readers to a specific page with the addition of #page=n to the document URL, where n is the page number. For example, using http://www.domain.com/document.pdf#page=5 as the citation URL displays page five of the document in any PDF viewer that supports this feature. If the viewer or browser does not support it, it will display the first page instead.

Linking to Google Books pages

Google Books sometimes allows numbered book pages to be linked to directly. Page links should only be added when the book is available for preview; they will not work with snippet view. Keep in mind that availability varies by location. No editor is required to add page links, but if another editor adds them, they should not be removed without cause; see the October 2010 RfC for further information.

These can be added in several ways (with and without citation templates):

In edit mode, the URL for p. 18 of A Theory of Justice can be entered like this using the {{Cite book}} template:

 to properly formatted footnote or Harvard-style references. Written in Ruby and requires a working installation with basic libraries.
  • pubmed2wikipedia.xsl an XSL stylesheet transforming the XML output of PubMed to Wikipedia refs.
  • Citation export tools

    You can insert a link beside each citation in Wikipedia, allowing you to export the citation to a reference manager such as EndNote. To install the script just add the following line to Special:MyPage/skin.js (applies to the currently selected skin) or Special:MyPage/common.js (applies to all skins)"

    importScript("User:Smith609/endnote.js");

    Then "Publish changes" and follow the instructions at the top of that page to bypass your browser's cache.

    Reference management software

    Reference management software can output formatted citations in several styles, including BibTeX, RIS, or Wikipedia citation template styles.

    Comparison of reference management software – side-by-side comparison of various reference management software
    Wikipedia:Citing sources with Zotero – essay on using Zotero to quickly add citations to articles. Zotero (by Roy Rosenzweig Center for History and New Media; license: Affero GPL) is open-source software with local reference database which can be synchronized between several computers over the online database (up to 300 MB without payment).
    EndNote (by Thomson Reuters; license: proprietary)
    Mendeley (by Elsevier; license: proprietary)
    Paperpile (by Paperpile, LLC; license: proprietary)
    Papers (by Springer; license: proprietary)

    See also

    How to cite

    Citation problems

    Changing citation style formats

    Notes

    1. ^ Words like citation and reference are used interchangeably on the English Wikipedia. On talk pages where the language can be more informal or in edit summaries or templates where space is a consideration, reference is often abbreviated ref with the plural refs. Footnote may refer specifically to citations using ref tag formatting or to explanatory text; endnotes specifically refers to citations placed at the end of the page. See also: Wikipedia:Glossary.
    2. ^ See this July 2007 discussion for more detail on why scrolling reference lists should not be used.

    Further reading

    External links

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