This page is a style guide, describing how to write citations in articles.

Wikipedia:Verifiability, which is policy, says that attribution is required for "direct quotes and for material that is challenged or likely to be challenged." Any material that is challenged, and for which no source is provided within a reasonable time (or immediately if it's about a living person), may be removed by any editor. For information about the importance of using good sources in biographies of living persons, see Wikipedia:Biographies of living persons, which is also policy.

If you don't know how to format a citation, provide as much information as you can, and others will help to write it correctly.

Why sources should be cited

Main articles: Wikipedia:Verifiability and Wikipedia:No original research

Wikipedia is by its very nature a work by people with widely different knowledge and skills. The reader needs to be assured that the material within it is reliable: this is especially important where statements are made about controversial issues. The purpose of citing your sources is:

• To improve the credibility of Wikipedia.
• To avoid claims of plagiarism.
• To show that your edit is not original research and to reduce editorial disputes.
• To ensure that the content of articles can be checked by any reader or editor.
• To help users find additional information on the topic.
• To ensure that material about living persons complies with Wikipedia:Biographies of living persons.

Use of terms

This guideline uses the terms "source," "reference," and "citation" interchangeably.

When to cite sources

When adding material that is challenged or likely to be challenged

Main article: Wikipedia:Verifiability

WP:V says: All material that is challenged or likely to be challenged needs a source.

The need for citations is especially important when writing about opinions held on a particular issue. Avoid weasel words where possible, such as, "Some people say ..." Instead, make your writing verifiable: find a specific person or group who holds that opinion and give a citation to a reputable publication in which they express that opinion. Remember that Wikipedia is not a place for expressing your own opinions or for original research.

Because this is the English Wikipedia, English-language sources should be given whenever possible, and should always be used in preference to other language sources of equal calibre. However, do give references in other languages where appropriate. If quoting from a different language source, an English translation should be given with the original-language quote beside it.

When quoting someone

Main article: Wikipedia:Verifiability

You should always add a citation when quoting published material, and the citation should be placed directly after the quotation, which should be enclosed within double quotation marks — "like this" — or single quotation marks if it is a quote-within-a-quote — "and here is such a 'quotation' as an example." For long quotes, you may wish to use Quotation templates.

When adding material to the biography of a living person

Main article: Wikipedia:Biographies of living persons

Biographies of living persons should be sourced with particular care, for legal and ethical reasons. All contentious material about living persons must cite a reliable source. Do not wait for another editor to request a source. If you find unsourced or poorly sourced contentious material about a living person — whether in an article or on a talk page — remove it immediately! Do not leave it in the article and ask for a source. Do not move it to the talk page. This applies whether the material is in a biography or any other article.

When checking content added by others

You can also add sources for material you did not write. Adding citations is an excellent way to contribute to Wikipedia. See Wikipedia:WikiProject Fact and Reference Check for organized efforts to add citations.

When uploading an image

Images must include source details and a copyright tag on the image description page. It is important that you list the author of the image if known (especially if different from the source), which is important both for copyright and for informational purposes. Some copyright licenses require that the original author receive credit for their work. If you download an image from the web, you should give the URL:

If you got the image from an offline source, you should specify:

Any image with a nonfree copyright license must be accompanied by a non-free use rationale (also called a fair use rationale) for each article in which the image is used.

How to cite sources

General references versus inline citations

Articles can be supported with references in two ways: the provision of general references – books or other sources that support a significant amount of the material in the article – and inline citations, which are mandated by the featured article and good article criteria. Inline citations are references within the text that provide source information for specific statements. They are needed for statements that are challenged or likely to be challenged, including contentious material about living persons, and for all quotations.

Say where you found the material

It is improper to copy a citation from an intermediate source without making clear that you saw only that intermediate source. For example, you might find some information on a web page which says it comes from a certain book. Unless you look at the book yourself to check that the information is there, your reference is really the web page, which is what you must cite. The credibility of your article rests on the credibility of the web page, as well as the book, and your article must make that clear.

Provide full citations

All citation techniques require detailed full citations to be provided for each source used. Full citations must contain enough information for other editors to identify the specific published work you used.

Full citations for books typically include: the name of the author, the title of the book or article, the date of publication, and page numbers. The name of the publisher, city of publication, and ISBN are optional. For journal articles, include volume number, issue number and page numbers. Citations for newspaper articles typically include the title of the article in quotes, the byline (author's name), the name of the newspaper in italics, date of publication, page number(s), and the date you retrieved it if it is online.

Provide page numbers

When citing books and articles, provide page numbers where appropriate. Page numbers should be included whenever possible in a citation that accompanies a specific quotation from, or a paraphrase or reference to, a specific passage of a book or article. The edition of the book should be included in the reference section, or included in the footnote, because pagination can change between editions. Page numbers are especially important in case of lengthy unindexed books. Page numbers are not required when a citation accompanies a general description of a book or article, or when a book or article, as a whole, is being used to exemplify a particular point of view.

Inline citation styles

Harvard referencing

For more details on this topic, see Wikipedia:Harvard referencing.

Under the Harvard referencing system, a book is cited in the text in parentheses, after the section, sentence, or paragraph for which the book was used as a source, using the surname of the author and the year of publication only, with the parentheses closing before the period, as in (Author 2005). These citations can be generated by using inline {{Harvard citation}} templates, though templates should be neither added nor removed against consensus.

A full citation is then placed at the end of the text in an alphabetized list of "References". If full citations use the {{Citation}} template, the Harvard citation as above will include an automatic link to the full citation. According to The Oxford Style Manual, the Harvard system is the "most commonly used reference method in the physical and social sciences" (Ritter 2002).

Page numbers must be included in a citation that accompanies a specific quotation from, or a paraphrase or reference to, a specific passage of a book or article. They usually follow the date in this way: (Author 2006:28).

In article, common variations:

• For two authors, use (Smith & Jones 2005); for more authors, use (Smith et al. 2005).
• If the same author has published two books in 1996, and both are being referenced in the text, this is written as (Clancy 1996a) and (Clancy 1996b).
• The specific page, section, or division of the cited work should usually follow the date in this way: (Author 2006:28).
• If the date of publication is unavailable, use "n.d." (meaning, no date)
• Newspaper articles may give the name of the newspaper and the date of publication after the sentence (The Guardian, December 17, 2005).

In a "References" section at the end of the article:

For an article: in the case of (Traynor 2005) or (The Guardian, December 17, 2005), this might be:

• Traynor, I. "Judge tells Ankara to decide on fate of leading author", The Guardian, December 17, 2005.

Footnotes

For more details on this topic, see Wikipedia:Footnotes.

What footnotes are used for

A footnote is a note placed at the bottom of a page to comment on a part of the main text, or to provide a reference (a source) for it. Footnotes are often used to add information that might be helpful to later fact-checkers, such as a quotation that supports your edit.

How to write them

The connection between the relevant text and its footnote is indicated by a number or symbol which appears both after the relevant text and before the footnote.

1. Place a <ref> ... </ref> where you want a footnote reference number to appear in an article—type the text of the note between the ref tags.
2. Place {{reflist}} or <references/> in an otherwise empty "Notes" or "References" section near the end of the article—the list of notes will be automatically generated here. If you want to create columns of notes, write {{reflist|2}}.

Example:

The Sun is pretty big,<ref>Miller, E: "The Sun", page 23. Academic Press, 2005</ref>
but the Moon is not so big.<ref>Smith, R: "Size of the Moon", ''Scientific American'', 46(78):46</ref>

== Notes ==
{{reflist}}

Result:

The Sun is pretty big, but the Moon is not so big.

Section headings

Recommended section names to use for footnotes in Wikipedia are:

• ==Notes==
• ==Footnotes==
• ==References==

Maintaining a "References" section in addition to "Notes"

When footnotes are used, it can be helpful to maintain a separate "References" section, in which the sources that were used are listed in alphabetical order. With articles that have lots of footnotes, it can become hard to see which sources have been used, particularly when the footnotes contain explanatory text. A References section helps readers to see at a glance the quality of the references used.

If such a section is included, the footnotes should be in a separate section entitled "Notes" or "Footnotes." Where an alphabetical list of references is provided, short footnotes may be used, giving the author(s) and the page number, and perhaps the title, but without a full citation.

Ref tags and punctuation

Some material must be referenced mid-sentence, but footnotes are usually placed at the end of a sentence or paragraph. Footnotes at the end of a sentence or phrase are normally placed immediately after the punctuation, except for dashes, as recommended by the Chicago Manual of Style. For example: President Bush called for a halt to the violence, and opposed a timetable for withdrawal. Some editors prefer the style of journals such as Nature, which place references before punctuation. If an article has evolved using predominantly one style of ref tag placement, the whole article should conform to that style unless there is a consensus to change it.

Notes

1. ^ Miller, E: "The Sun", page 23. Academic Press, 2005
2. ^ Smith, R: "Size of the Moon", Scientific American, 46(78):46
3. ^ The Chicago Manual of Style, 14th ed. 1993, Clause 15.8, p. 494 - "The superior numerals used for note reference numbers in the text should follow any punctuation marks except the dash, which they precede. The numbers should also be placed outside closing parentheses."
4. ^ example footnote abc
5. ^ example footnote xyz

Embedded links

For more details on this topic, see Wikipedia:Embedded citations.

Web pages referenced in an article can be linked to directly by enclosing the URL in square brackets. For example, a reference to a newspaper article can be embedded like: , which looks like this:

A full citation is also required in a References section at the end of the article.

*Plunkett, John. , ''The Guardian'', ] ]. Accessed ] ].

which appears as:

• Plunkett, John. "Sorrell accuses Murdoch of panic buying", The Guardian, October 27, 2005. Accessed October 27, 2005.

Citation templates

For more details on this topic, see Wikipedia:Citation templates.

The use of citation templates is neither encouraged nor discouraged. Templates may be used at the discretion of individual editors, subject to agreement with other editors on the article. Some editors find them helpful, arguing that they maintain a consistent style across articles, while other editors find them distracting when used inline in the text, because they make the text harder to read in edit mode and harder to edit. Because templates are optional and can be contentious, editors should not change an article with a distinctive citation format to another without gaining consensus.

Further reading/External links

An ==External links== or ==Further reading== or ==Bibliography== section is placed near the end of an article and offers books, articles, and links to websites related to the topic that might be of interest to the reader. The section "Further reading" may include both online material and material not available online. If all recommended material is online, the section may be titled "External links".

All items used as sources in the article must be listed in the "References" or "Notes" section, and are usually not included in "Further reading" or "External links". However, if an item used as a reference covers the topic beyond the scope of the article, and has significant usefulness beyond verification of the article, you may want to include it here as well. This also makes it easier for users to identify all the major recommended resources on a topic. The Wikipedia guideline for external links that are not used as sources can be found here.

Convenience links

A "convenience link" is a link to source material on the Web posted by someone other than the original publisher or author. For example, a newspaper article no longer available on the newspaper's website may be hosted elsewhere too. When offering convenience links, it is important to be reasonably certain that the convenience copy is a true copy of the original, without any changes or inappropriate commentary. Accuracy can be assumed when the hosting website appears reliable, but otherwise editors should exercise caution.

Where several sites host a copy of the material, the site selected as the convenience link should be the one whose general content appears most in line with Wikipedia:Neutral point of view and Wikipedia:Verifiability.

Scrolling lists

Scrolling lists, for example of references, should never be used because of issues with readability, accessibility, printing, and site mirroring. Additionally, it cannot be guaranteed that such lists will display properly in all web browsers.

Dealing with citation problems

Unsourced material

Main article: WP:PROVEIT

If an article has no references, and you are unable to find them yourself, you can tag the article with the template {{Unreferenced}}, so long as the article is not nonsensical or a BLP, in which case request admin assistance. If a particular claim in an article lacks citation and is doubtful, consider placing {{fact}} after the sentence or removing it. Consider the following in deciding which action to take:

1. If it is doubtful but not harmful to the whole article or to Wikipedia, use the {{fact}} tag, but remember to go back and remove the claim if no source is produced within a reasonable time.

2. If it is doubtful and harmful, you should remove it from the article; you may want to move it to the talk page and ask for a source, unless you regard it as very harmful or absurd, in which case it should not be posted to a talk page either. Use your common sense. All unsourced and poorly sourced contentious material about living persons should be removed from articles and talk pages immediately. It should not be tagged. See Wikipedia:Biographies of living persons and Wikipedia:Libel.

What to do when a reference link "goes dead"

When a link in the References section or Notes section "goes dead" (see link rot), it should be repaired or replaced if possible, but the citation need not be deleted. External links/Further reading sections are not as important, but bad links in those sections should also be fixed. Often, a live substitute link can be found. In most cases, one of the following approaches will preserve an acceptable citation:

• If the link was merely a "convenience link" to an online copy of material that originally appeared in print, and an appropriate substitute cannot be found, drop the link but keep the citation.
• Some pages can be recovered from the Internet Archive or WebCite. Go to http://www.webarchive.org/ or http://www.webcitation.org, respectively, and search for the old link by URL. Make sure that your new citation mentions the date the page was archived by the Internet Archive. In the case of WebCite, any broken URL can be searched for and replaced using the format http://www.webcitation.org/query?url=URL&date=DATE, where URL is the URL that is broken and needs to be restored. The DATE variable is optional and indicates the (approximate) caching date. For example, http://www.webcitation.org/query?url=www.pewinternet.org/pdfs/PIP_Health_Report_July_2003.pdf&date=2005-12-31 retrieves a copy of the URL http://www.pewinternet.org/pdfs/PIP_Health_Report_July_2003.pdf which is closest to the date of Dec 31st, 2005 (in this example, the actual caching date was 21 days before the requested date). WebCite allows on-demand prospective archiving and is not crawler-based; i.e. pages are only archived if the author has requested archiving when he cited the piece for the first time, which is highly recommended
• If it was a link to web-only material, it may be worth the effort to search the target site for an equivalent page at a new location, an indication that the whole site has moved, etc.
• If you cannot find the page on the Internet Archive, remember that you can often find recently deleted pages in Google's cache. They will not be there long, and it is no use linking to them, but this may let you find the content, which can be useful in finding an equivalent page elsewhere on the Internet and linking to that.

If none of those strategies succeed, the cited material and citation should be removed if the material is contentious or concerns a living person. Otherwise, if the cited material is retained, record in the citation the date that the original link was found to be inactive — even inactive, it still records the sources that were used, and it is possible hard copies of such references may exist, or alternatively that the page will turn up in the near future in the Internet Archive, which lags by six months or more.

Some source material, especially scientific papers, can be cited using a digital object identifier, by linking through dx.doi.org. This will allow citation links to remain intact even if the URL changes.

Tools

• WebCite - tool to archive webpages to allow stable citation links.
• Template builder — Given an ISBN, a PubMed ID, etc., output a citation which can be pasted into a Wikipedia article.
• Reference generator — generates /www.jigfo.comcode for journals, webpages, and other commonly cited sources.
• WPCITE - Firefox add-in for one-click creation of partial {{cite news}} information, in footnote format. See the developer's page for details.
• User:CitationTool - tool for finding citation errors and fixing them.
• User:Fictional tool - tool for cleaning up web citations
• Wikicite is a free program that helps editors to properly reference their Wikipedia contributions using citation templates. It is written in Visual Basic .NET, making it suitable only for users with the .NET Framework installed on Windows, or, for other platforms, the Mono alternative framework. Wikicite and its source code is freely available, see the developer's page for further details.
• OttoBib.com is a free tool to generate an alphabetized bibliography for books, using an input list of International Standard Book Number (ISBN) numbers, with output in MLA, APA, Chicago/Turabian, BibTeX, or Wikipedia format (also generates a permalink).
• Zotero allows you to find articles in Mozilla Firefox and easily paste them into Wikipedia as citation templates using Ctrl-Alt-C
• Verisimilus's Cite generation page lets you find articles using built-in Google Scholar interface and automatically produce an appropriate cite template. It also features a BibTeX to {{cite}} converter.

See also

• Wikipedia:Citation templates - a full listing of various styles for citing all sorts of materials.
• Wikipedia:Scientific citation guidelines – guidelines for dealing with scientific and mathematical articles.
• Wikipedia:Copyright problems – in case of text that has been copied verbatim inappropriately.
• Wikipedia:Citing sources/example style – listing several examples of APA and Harvard referencing techniques.
• Wikipedia:Referencing for beginners A simple practical guide to getting started.

Notes

1. ^ Miller, E: "The Sun", page 23. Academic Press, 2005
2. ^ Smith, R: "Size of the Moon", Scientific American, 46(78):46
3. ^ The Chicago Manual of Style, 14th ed. 1993, Clause 15.8, p. 494 - "The superior numerals used for note reference numbers in the text should follow any punctuation marks except the dash, which they precede. The numbers should also be placed outside closing parentheses."
4. ^ example footnote abc
5. ^ example footnote xyz

References

• Concordia Libraries (Concordia University). Citation and Style Guides. Retrieved December 28, 2004. (This provides a list of common citation styles.)
• Citation Styles Handbook: APA
• Citation Styles Handbook: MLA
• APA Style.org
• Using American Psychological Association (APA) Format (Updated to 5th Edition)
• Citing Electronic Documentation (APA, Chicago, MLA)
• The Columbia Guide to Online Style
• Ritter, R. (2002). The Oxford Style Manual. Oxford University Press. ISBN 0-19-860564-1
• University of Chicago Press Staff. (2003). The Chicago Manual of Style, 15th edition. University Of Chicago Press. ISBN 0-226-10403-6