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 Help:Referencing for beginners", for a brief introduction on how to put references in Wikipedia articles; and cite templates in Visual Editor, about a graphical way for citation, included in Wikipedia.. 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: "
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.
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).
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.
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 short citations, then the inline citations will refer to this information in abbreviated form, as described in the relevant sections above.)
Citations for individually authored chapters in books typically include:
Do not cite an entire body of work by one performer. Instead, make one citation for each work your text relies on.
Citations for films, TV episodes, or video recordings typically include:
When citing lengthy sources, you should identify which part of a source is being cited.
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.
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.
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:IARC Monographs On The Evaluation Of Carcinogenic Risks To Humans – Doxefazepam
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.
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.
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):
When the page number is a Roman numeral, commonly seen at the beginning of books, the URL looks like this for (Roman numeral 17) of the same book:
The &pg=PR17 indicates "page, Roman, 17", in contrast to the &pg=PA18, "page, Arabic, 18" the URL given earlier.
You can also link to a tipped-in page, such as an unnumbered page of images between two regular pages. (If the page contains an image that is protected by copyright, it will be replaced by a tiny notice saying "copyrighted image".) The URL for of The Selected Papers of Elizabeth Cady Stanton and Susan B. Anthony, looks like this:
The &pg=PA304-IA11 can be interpreted as "page, Arabic, 304; inserted after: 11".
Users may also link the quotation on Google Books to individual titles, via a short permalink which ends with their related ISBN, OCLC or LCCN numerical code, e.g.:
http://books.google.com/books?vid=ISBN0521349931, a permalink to the Google book with the ISBN code 0521349931.
For further details, you may see on support.google.com.
"Say where you read it" follows the practice in academic writing of citing sources directly only if you have read the source yourself. If your knowledge of the source is secondhand—that is, if you have read Jones (2010), who cited Smith (2009), and you want to use what Smith (2009) said—make clear that your knowledge of Smith is based on your reading of Jones.
When citing the source, write the following (this formatting is just an example):
John Smith (2009). Name of Book I Haven't Seen, Cambridge University Press, p. 99, cited in Paul Jones (2010). Name of Encyclopedia I Have Seen, Oxford University Press, p. 29.
Note: The advice to "say where you read it" does not mean that you have to give credit to any search engines, websites, libraries, library catalogs, archives, subscription services, bibliographies, or other sources that led you to Smith's book. If you have read a book or article yourself, that's all you have to cite. You do not have to specify how you obtained and read it.
So long as you are confident that you read a true and accurate copy, it does not matter whether you read the material using an online service like Google Books; using preview options at a bookseller's website like Amazon; through your library; via online paid databases of scanned publications, such as JSTOR; using reading machines; on an e-reader (except to the extent that this affects page numbering); or any other method.
Editors should be aware that older sources (especially those in the public domain) are sometimes reprinted with modern publication dates. When this occurs and the citation style being used requires it, cite both the original publication date, as well as the date of the re-publication, e.g.:
Alternately, information about the reprint can be appended as a textual note:
Publication dates, for both older and recent sources, should be written with the goal of helping the reader find the publication and, once found, confirm that the correct publication has been located. For example, if the publication date bears a date in the Julian calendar, it should not be converted to the Gregorian calendar.
If the publication date was given as a season or holiday, such as "Winter" or "Christmas" of a particular year or two-year span, it should not be converted to a month or date, such as July–August or December 25. If a publication provided both seasonal and specific dates, prefer the specific one.
In most cases it is sufficient for a citation footnote simply to identify the source (as described in the sections above); readers can then consult the source to see how it supports the information in the article. Sometimes, however, it is useful to include additional annotation in the footnote, for example to indicate precisely which information the source is supporting (particularly when a single footnote lists more than one source – ).
A footnote may also contain a relevant exact quotation from the source. This is especially helpful when the cited text is long or dense. A quotation allows readers to immediately identify the applicable portion of the reference. Quotes are also useful if the source is not easily accessible.
In the case of non-English sources, it may be helpful to quote from the original text and then give an English translation. If the article itself contains a translation of a quote from such a source (without the original), then the original should be included in the footnote.
Inline citations allow the reader to associate a given bit of material in an article with the specific reliable source(s) that support it. Inline citations are added using either footnotes (long or short) or parenthetical references. This section describes how to add either type, and also describes how to create a list of full bibliography citations to support shortened footnotes.
The first editor to add footnotes to an article must create a section where those citations are to appear.
This section, if needed, is usually titled "Notes" or "References", and is placed at or near the bottom of the article. For more about the order and titles of sections at the end of an article (which may also include "Further reading" and "External links" sections), see Wikipedia:Footers.
The footnotes will then automatically be listed under that section heading. Each numbered footnote marker in the text is a clickable link to the corresponding footnote, and each footnote contains a caret that links back to the corresponding point in the text.
Scrolling lists, or lists of citations appearing within a scroll box, should never be used. This is because of issues with readability, browser compatibility, accessibility, printing, and site mirroring.[note 2]
If an article contains a list of general references, this is usually placed in a separate section, titled (for example) "References". This usually comes immediately after the section(s) listing footnotes, if any. (If the general references section is called "References", then the citations section is usually called "Notes".)
To create a footnote, use the
<ref>...</ref> syntax at the appropriate place in the article text, for example:
It will also be necessary to generate the list of footnotes (where the citation text is actually displayed); for this, see the previous section.
As in the above example, citation markers are normally placed after adjacent punctuation such as periods (full stops) and commas. For exceptions, see the WP:Manual of Style § Punctuation and footnotes. Note also that no space is added before the citation marker. Citations should not be placed within, or on the same line as, section headings.
The citation should be added close to the material it supports, offering text–source integrity. If a word or phrase is particularly contentious, an inline citation may be added next to that word or phrase within the sentence, but it is usually sufficient to add the citation to the end of the clause, sentence, or paragraph, so long as it's clear which source supports which part of the text.
If an article contains both footnoted citations and other (explanatory) footnotes, then it is possible (but not necessary) to divide them into two separate lists using footnotes groups. The explanatory footnotes and the citations are then placed in separate sections, called (for example) "Notes" and "References" respectively.
Inline references can significantly bloat the wikitext in the edit window and can become difficult to manage and confusing. There are two main methods to avoid clutter in the edit window:
As with other citation formats, articles should not undergo large-scale conversion between formats without consensus to do so.
Note, however, that references defined in the reference list template can no longer be edited with the VisualEditor.
For multiple use of the same inline citation or footnote, you can use the named references feature, choosing a name to identify the inline citation, and typing
<ref name="name">text of the citation</ref>. Thereafter, the same named reference may be reused any number of times either before or after the defining use by typing the previous reference name, like this:
<ref name="name" />. The use of the slash before the
> means that the tag is self-closing, and the
</ref> used to close other references must not be used in addition.
The text of the
name can be almost anything—apart from being completely numeric. If spaces are used in the text of the
name, the text must be placed within double quotes. Placing all named references within double quotes may be helpful to future editors who do not know that rule. To help with page maintenance, it is recommended that the text of the
name have a connection to the inline citation or footnote, for example "author year page":
<ref name="Smith 2005 p94">text of the citation</ref>.
Use straight quotation marks
" to enclose the reference name. Do not use curly quotation marks
“”. Curly marks are treated as another character, not as delimiters. The page will display an error if one style of quotation marks is used when first naming the reference, and the other style is used in a repeated reference, or if a mix of styles is used in the repeated references.
When an article cites many different pages from the same source, to avoid the redundancy of many big, nearly identical full citations, most Wikipedia editors use one of these options:
Please combine precisely duplicated full citations, in keeping with the existing citation style (if any). In this context "precisely duplicated" means having the same content, not necessarily identical strings ("The New York Times" is the same as "NY Times"; different access-dates are not significant). Do not discourage editors, particularly inexperienced ones, from adding duplicate citations when the use of the source is appropriate, because a duplicate is better than no citation. But any editor should feel free to combine them, and doing so is the best practice on Wikipedia.
Citations to different pages or parts of the same source can also be combined (preserving the distinct parts of the citations), as described in the previous section. Any method that is consistent with the existing citation style (if any) may be used, or consensus can be sought to change the existing style.
The tool Wikipedia:AutoWikiBrowser (AWB) will identify and (usually) correct exact duplicates between <ref>...</ref> tags. Finding duplicate citations by examining reference lists is difficult; there is a tool that helps to identify Web citations with the exact same URL but not necessarily exact duplicates: . It is not a Wikipedia tool, and simply lists duplicated URLs found in a Web page, and will unnecessarily include URLs that are not in citations (e.g., in an infobox). As it processes only the URL, not the whole citation, it will successfully find non-exact duplicates with the same URL, for example one using
first=, the other
author=. Note that displaying only exact duplicate URLs will not identify URLs which might have the same reference followed by different non-significant tracking parameters such as
?utm_source=google&utm_medium=...&utm_term=...&utm_campaign=...., though in practice most duplicate Web references have identical URLs.
The URL Extractor tool has three steps. To use it, enter the URL of the Wikipedia article in Step 1 and click "Load", untick "Remove duplicate addresses" and tick "Only Display duplicate URL addresses" in Step 2, and click Extract in Step 3; a list of URLs which are duplicated, with some false positives, will be displayed. With this list, the citations can be searched for in the article and merged manually where appropriate. Some judgement and work may be required; there may be references duplicated but with different names which must be handled, one live reference may include an archive-url while a duplicate does not, references with the same URL may cite different page numbers, and so on. As always it is the responsibility of the editor to check that references are not incorrectly merged.
Some Wikipedia articles use short citations, giving summary information about the source together with a page number, as in
<ref>Smith 2010, p. 1.</ref>. These are used together with full citations, which give full details of the sources, but without page numbers, and are listed in a separate "References" section.
Shortened notes using titles rather than publication dates would look like this in the article:
When using manual links it is easy to introduce errors such as duplicate anchors and unused references. The script User:Ucucha/HarvErrors will show many related errors. Duplicate anchors may be found by using the W3C Markup Validation Service.
While most articles use footnote citations as described in the above sections, some articles use a parenthetical referencing style. Here, short citations in parentheses, such as (Smith 2010, p. 1), are placed within the article text itself. Full details of each source used are given in a full citation, e.g., Smith, John. Name of Book. Cambridge University Press, 2010. The full citations are listed in alphabetical order, according to the authors' surnames, at the end of the article in a "References" section.
Short citations that use
<ref> tags are not parenthetical references; see the section on short citations above for that method. The inline citation and full citation may be linked using a template; as with other citation templates, these should not be added to articles without consensus.
Notice that, unlike footnotes, parenthetical references are placed before adjacent punctuation such as commas and periods.
While citations should aim to provide the information listed above, Wikipedia does not have a single house style, though citations within any given article should follow a consistent style. A number of citation styles exist including those described in the Wikipedia articles for Citation, APA style, ASA style, MLA style, The Chicago Manual of Style, Author-date referencing, the Vancouver system and Bluebook.
Although nearly any consistent style may be used, avoid all-numeric date formats other than YYYY-MM-DD, because of the ambiguity concerning which number is the month and which the day. For example, 2002-06-11 may be used, but not 11/06/2002. The YYYY-MM-DD format should in any case be limited to Gregorian calendar dates where the year is after 1582. Because it could easily be confused with a range of years, the format YYYY-MM is not used.
Editors should not attempt to change an article's established citation style merely on the grounds of personal preference, to make it match other articles, or without first seeking consensus for the change. The arbitration committee ruled in 2006:
Wikipedia does not mandate styles in many different areas; these include (but are not limited to) American vs. British spelling, date formats, and citation style. Where Wikipedia does not mandate a specific style, editors should not attempt to convert Wikipedia to their own preferred style, nor should they edit articles for the sole purpose of converting them to their preferred style, or removing examples of, or references to, styles which they dislike.
As with spelling differences, it is normal practice to defer to the style used by the first major contributor or adopted by the consensus of editors already working on the page, unless a change in consensus has been achieved. If the article you are editing is already using a particular citation style, you should follow it; if you believe it is inappropriate for the needs of the article, seek consensus for a change on the talk page. If you are the first contributor to add citations to an article, you may choose whichever style you think best for the article.
If all or most of the citations in an article consist of bare URLs, or otherwise fail to provide needed bibliographic data – such as the name of the source, the title of the article or web page consulted, the author (if known), the publication date (if known), and the page numbers (where relevant) – then that would not count as a "consistent citation style" and can be changed freely to insert such data. The data provided should be sufficient to uniquely identify the source, allow readers to find it, and allow readers to initially evaluate it without retrieving it.
As noted above under "What information to include", it is helpful to include hyperlinks to source material, when available. Here we note some issues concerning these links.
Embedded links to external websites should not be used as a form of inline citation, because they are highly susceptible to linkrot. Wikipedia allowed this in its early years—for example by adding a link after a sentence, like this: [http://media.guardian.co.uk/site/story/0,14173,1601858,00.html], which is rendered as: . This is no longer recommended. Raw links are not recommended in lieu of properly written out citations, even if placed between ref tags, like this . Since any citation that accurately identifies the source is better than none, do not revert the good-faith addition of partial citations. They should be considered temporary, and replaced with more complete, properly formatted citations as soon as possible.
Embedded links should never be used to place external links in the content of an article, like this: " announced their latest product ...".
A convenience link is a link to a copy of your source on a web page provided by someone other than the original publisher or author. For example, a copy of a newspaper article no longer available on the newspaper's website may be hosted elsewhere. 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, and that it does not infringe the original publisher's copyright. Accuracy can be assumed when the hosting website appears reliable.
For academic sources, the convenience link is typically a reprint provided by an open-access repository, such as the author's university's library or institutional repository. Such green open access links are generally preferable to paywalled or otherwise commercial and unfree sources.
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.
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.
For a source available in hardcopy, microform, and/or online, omit, in most cases, which one you read. While it is useful to cite author, title, edition (1st, 2nd, etc.), and similar information, it generally is not important to cite a database such as ProQuest, EBSCOhost, or JSTOR (see the list of academic databases and search engines) or to link to such a database requiring a subscription or a third party's login. The basic bibliographic information you provide should be enough to search for the source in any of these databases that have the source. Don't add a URL that has a part of a password embedded in the URL. However, you may provide the DOI, ISBN, or another uniform identifier, if available. If the publisher offers a link to the source or its abstract that does not require a payment or a third party's login for access, you may provide the URL for that link. If the source only exists online, give the link even if access is restricted (see WP:PAYWALL).
To help prevent dead links, persistent identifiers are available for some sources. Some journal articles have a digital object identifier (DOI); some online newspapers and blogs, and also Wikipedia, have permalinks that are stable. When permanent links aren't available, consider archiving the referenced document when writing the article; on-demand web archiving services such as the Wayback Machine () or archive.today () are fairly easy to use (see pre-emptive archiving).
Do not delete a citation merely because the URL is not working. Dead links should be repaired or replaced if possible. If you encounter a dead URL being used as a reliable source to support article content, follow these steps prior to deleting it:
|access-date=. If that parameter is not specified, a can be performed to determine when the link was added to the article.
|url-status=usurpedto hide the original website link in the citation.
When using inline citations, it is important to maintain text–source integrity. The point of an inline citation is to allow readers and other editors to check that the material is sourced; that point is lost if the citation is not clearly placed. The distance between material and its source is a matter of editorial judgment, but adding text without clearly placing its source may lead to allegations of original research, of violations of the sourcing policy, and even of plagiarism.
Editors should exercise caution when rearranging or inserting material to ensure that text–source relationships are maintained. References need not be moved solely to maintain the chronological order of footnotes as they appear in the article, and should not be moved if doing so might break the text–source relationship.
If a sentence or paragraph is footnoted with a source, adding new material that is not supported by the existing source to the sentence/paragraph, without a source for the new text, is highly misleading if placed to appear that the cited source supports it. When new text is inserted into a paragraph, make sure it is supported by the existing or a new source. For example, when editing text originally reading
an edit that does not imply that the new material is sourced by the same reference is
Do not add other facts or assertions into a fully cited paragraph or sentence:
Include a source to support the new information. There are several ways to write this, including:
Sometimes the article is more readable if multiple citations are bundled into a single footnote. For example, when there are multiple sources for a given sentence, and each source applies to the entire sentence, the sources can be placed at the end of the sentence, like this. Or they can be bundled into one footnote at the end of the sentence or paragraph, like this.
Bundling is also useful if the sources each support a different portion of the preceding text, or if the sources all support the same text. Bundling has several advantages:
For multiple citations in a single footnote, each in reference to specific statements, there are several layouts available, as illustrated below. Within a given article only a single layout should be used.
The sun is pretty big, but the moon is not so big. The sun is also quite hot.
In-text attribution is the attribution inside a sentence of material to its source, in addition to an inline citation after the sentence. In-text attribution should be used with direct speech (a source's words between quotation marks or as a block quotation); indirect speech (a source's words modified without quotation marks); and close paraphrasing. It can also be used when loosely summarizing a source's position in your own words. It avoids inadvertent plagiarism and helps the reader see where a position is coming from. An inline citation should follow the attribution, usually at the end of the sentence or paragraph in question.
N To reach fair decisions, parties must consider matters as if behind a veil of ignorance.
When using in-text attribution, make sure it doesn't lead to an inadvertent neutrality violation. For example, the following implies parity between the sources, without making clear that the position of Darwin is the majority view:
Neutrality issues apart, there are other ways in-text attribution can mislead. The sentence below suggests The New York Times has alone made this important discovery:
N According to The New York Times, the sun will set in the west this evening.
It is preferable not to clutter articles with information best left to the references. Interested readers can click on the ref to find out the publishing journal:
N In an article published in The Lancet in 2012, researchers announced the discovery of the new tissue type.
Y The discovery of the new tissue type was first published by researchers in 2012.
Simple facts such as this can have inline citations to reliable sources as an aid to the reader, but normally the text itself is best left as a plain statement without in-text attribution:
Y By mass, oxygen is the third most abundant element in the universe after hydrogen and helium.
A general reference is a citation to a reliable source that supports content, but is not linked to any particular text in the article through an inline citation. General references are usually listed at the end of the article in a "References" section, and are usually sorted by the last name of the author or the editor. General reference sections are most likely to be found in underdeveloped articles, especially when all article content is supported by a single source. The disadvantage of general references is that text–source integrity is lost, unless the article is very short. They are frequently reworked by later editors into inline citations.
The appearance of a general references section is the same as those given above in the sections on short citations and parenthetical references. If both cited and uncited references exist, their distinction can be highlighted with separate section names, e.g., "References" and "General references".
Citation templates can be used to format citations in a consistent way. The use of citation templates is neither encouraged nor discouraged: an article should not be switched between templated and non-templated citations without good reason and consensus – see "Variation in citation methods", above.
If citation templates are used in an article, the parameters should be accurate. It is inappropriate to set parameters to false values to cause the template to render as if it were written in some style other than the style normally produced by the template (e.g., MLA style).
Citations may be accompanied by metadata, though it is not mandatory. Most citation templates on Wikipedia use the COinS standard. Metadata such as this allow browser plugins and other automated software to make citation data accessible to the user, for instance by providing links to their library's online copies of the cited works. In articles that format citations manually, metadata may be added manually in a span, according to the .
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)"
Then "Publish changes" and follow the instructions at the top of that page to bypass your browser's cache.