Wikipedia:Citing sources
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This page is considered a style guideline on Wikipedia. It is generally accepted among editors and is considered a standard that users should follow. However, it is not set in stone and should be treated with common sense and the occasional exception. When editing this page, please ensure that your revision reflects consensus. When in doubt, discuss first on this page's talk page. |
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This page in a nutshell: Material challenged or likely to be challenged needs a reliable source. This page explains how to write the citations. |
| Wikipedia policy |
|---|
| Article standards |
| Neutral point of view Verifiability No original research Biographies of living persons |
| Working with others |
| Civility Consensus No personal attacks Dispute resolution |
| Global principles |
| What Wikipedia is not Ignore all rules |
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 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 policy.
If you do not know how to format the citation, provide as much information as you can; others can remove unneeded information, but can't fabricate information to make up a deficient citation.
[edit] Why sources should be cited
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 overall credibility and authoritative nature of Wikipedia.
- To credit a source for providing useful material and to avoid claims of plagiarism.
- To show that your edit is not original research.
- To ensure that the content of articles is credible and can be checked by any reader or editor.
- To help users find additional information on the topic.
- To reduce the likelihood of editorial disputes, or to resolve any that arise.
- To ensure that material about living persons complies with Wikipedia:Biographies of living persons.
[edit] When to cite sources
[edit] When you add content
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.
[edit] When adding material to the biography of a living person
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.
[edit] When you quote someone
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.
[edit] Images
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:
- Source: Downloaded from http://news.bbc.co.uk/1/hi/world/europe/4280841.stm
If you got the image from an offline source, you should specify:
- Source: Scanned from public record #5253 on file with Anytown, Somestate public surveyor
[edit] When you check 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:Forum for Encyclopedic Standards and Wikipedia:WikiProject Fact and Reference Check for organized efforts to add citations.
[edit] How to cite sources
- Further information: Wikipedia:Citing sources/example style
If you do not know how to format the citation, provide as much information as you can; others can reformat or remove information, but can't fabricate information to make up a deficient citation.
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, that is, references within the text, which provide source information for specific statements. Inline citations are needed for statements that are challenged or likely to be challenged, including contentious material about living persons, and for all quotations.
[edit] Say where you got it
It is improper to copy a citation from an intermediate source without making it clear that you saw only that intermediate source. For example, you might find 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 the article rests on the credibility of the web page, as well as the book, and the article itself must make that clear.
When citing books and articles, provide page numbers where appropriate. 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. 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.
[edit] Full references
All citation techniques require detailed full references to be provided for each source used. Full references must contain enough information for other editors to identify the specific published work you used.
Full references 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. References 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.
For two books by the same author, published the same year, using Harvard referencing, this might be:
- Clancy, T. (1996a). Executive Orders. New York: G.P. Putnam's Sons. ISBN 0-399-14218-5
- Clancy, T. (1996b). Marine. New York: Berkley Books. ISBN 0-425-15454-8
If the article in which the preceding examples appeared used footnote referencing rather than Harvard referencing, the letter after the year would be omitted.
In the Harvard system, full references appear at the end of the article in a section labeled "References." With the footnotes system, full references may also appear in a section labeled "References" or may appear in a mixed "Notes and references" section.
[edit] Full reference templates
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For more details on this topic, see Wikipedia:Citation templates.
Various templates can be used to help format full references more consistently. Templates exist for specific formats, such as {{cite journal}}, {{cite book}}, {{cite web}} and {{cite news}}. There is also a generic {{Citation}} template.
The use of templates is neither encouraged nor discouraged by this or any other guideline. 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 help maintain a consistent citation format across articles, while other editors find them unnecessary, arguing that they are distracting, particularly when used inline in the article text, as they make the text harder to read in edit mode and therefore harder to edit.
[edit] Inline citations
There are basically three inline citation methods used within Wikipedia.
- Embedded links
- Harvard referencing (also known as author-date referencing)
- Footnote referencing
Some of the features of Harvard referencing can be combined with footnote referencing—effectively resulting in a hybrid method.
- Short footnote citations with full references
[edit] Embedded links
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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: [http://media.guardian.co.uk/site/story/0,14173,1601858,00.html], which looks like this: [1]
As with all inline citation methods, a full reference would also be required in a "References" section at the end of the article, e.g.
- Plunkett, John. "Sorrell accuses Murdoch of panic buying", The Guardian, October 27, 2005. Accessed October 27, 2005.
Because of the difficulties in associating them with their appropriate full references, the use of embedded links for inline citations is not particularly recommended as a method of best practice.
[edit] Harvard referencing
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For more details on this topic, see Wikipedia:Harvard referencing.
According to The Oxford Style Manual, the Harvard system is the "most commonly used reference method in the physical and social sciences" (Ritter 2002). Under the Harvard referencing system, parenthesized author-date summary references are included with respect to sentences or paragraphs in the article text to which they apply. These references use the surname of the author, the year of publication and, where applicable, page or section references, for the source work.
Parentheses close before the period, as in (Author 2005). 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, p. 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, p. 28) or (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 cases where the author is unknown:
- If the article is written for an organization or periodical then use its name, as in (Department of Transport 2001) or (National Geographic 2005),
- otherwise, use the article title, italicized, as in (Advertising in the Western Cape 1990, p. 14).
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. Retrieved on 2007-11-23.
[edit] Harvard referencing templates
Inline author-date citations can be generated in the article text using {{Harvard citation}} templates. Use of the Harvard citation templates can include an automatic link to the full reference, but only if the full reference uses the {{Citation}} template. Links are not generated to full references using other templates or those written freehand.
Links can be created using {{wikiref}} and {{wikicite}} templates to work more generally between any inline article text citation and any format full reference, including the {{Citation}} template, any of the other formal templates such as {{cite journal}}, {{cite book}}, {{cite web}}, {{cite news}}, or any freehand written citations.
Wikiref can use a simple wikilink style format, as in the following example:
The Sun is pretty big ([[#Reference-idMiller2005|Miller 2005]], p. 23),
however the Moon is not so big ([[#Reference-idSmith2006|Smith 2006]], p. 46).
== References ==
*{{wikicite|id=idMiller2005|reference=Miller, E (2005). "The Sun", Academic Press.}}
*{{wikicite|id=idSmith2006|reference=Smith, R (2006). "Size of the Moon", Scientific American, 51(78).}}
Result:
The Sun is pretty big (Miller 2005, p. 23), however the Moon is not so big (Smith 2006, p. 46).
References (Harvard example)
- Miller, E (2005). "The Sun", Academic Press.
- Smith, R (2006). "Size of the Moon", Scientific American, 51(78).
[edit] Footnote referencing
- For more details on the more general topic of Wikipedia footnotes, see Wikipedia:Footnotes.
A footnote is a note placed at the bottom of a page of a document to comment on a part of the main text, or to provide a reference for it, or both. 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 reference.
- Place a <ref> ... </ref> where you want a footnote reference number to appear in an article—type the text of the reference between the ref tags.
- Place the <references/> tag in "References" section near the end of the article—the list of references will be generated here.
Example:
The Sun is pretty big,<ref>Miller, E: "The Sun", page 23. Academic Press, 2005</ref>
however the Moon is not so big.<ref>Smith, R: "Size of the Moon", ''Scientific American'', 51(78):46</ref>
== References ==
<references/>
Result:
The Sun is pretty big,[1] however the Moon is not so big.[2]
References (footnotes example)
- ^ Miller, E: "The Sun", page 23. Academic Press, 2005
- ^ Smith, R: "Size of the Moon", Scientific American, 51(78):46
When citing a website within the REF tags, do not use brackets only around the URL. For instance, <ref>[www.google.com]</ref> will result in the footnote being displayed as [1]. Thus, a numbered footnote's description is another number. Instead, cite the URL with a name, <ref>[www.google.com Google]</ref> to display the website page title in the reference list.
[edit] Where to place ref tags
- Further information: Wikipedia:Footnotes#Where to place ref tags
Some words, phrases or facts must be referenced mid-sentence, while others are referenced at the end. Frequently, a reference tag will coincide with punctuation and many editors put the reference tags after punctuation (except dashes), as is recommended by the Chicago Manual of Style (CMoS).[3] Some editors prefer the style of journals such as Nature which place references before punctuation. Each article should be internally consistent.
[edit] Section headings for footnote referencing
When footnotes are used solely to support references then the section name ==References== is recommended. When footnotes have a mix of commentary notes as well as references then the section name ==Notes and references== may be used.[i]
[edit] Short footnote citations with full references
A list of fully-formatted references ordered alphabetically by author surname will be properly included with Harvard style referencing in a "References" section. The inclusion of such an ordered section is seen as one of the advantages of that author-date referencing method. It helps the reader to determine exactly which sources have been used.
Rather than alphabetically, footnotes are simply listed in the same order in which the references were initially tagged in the article text. However, a separate alphabetized reference section can also be included along with the footnotes method. Where an ordered alphabetical list of fully-formatted references is maintained in a separate "References" section, then short citations may be used in footnotes. That is, without giving a fully-formatted reference in the footnotes, instead the footnotes contain only author, year and page number, so the footnotes then list citations in much the same format as the Harvard referencing method (only without the parenthesis of course). This in effect makes short footnote citations a hybrid method that combines aspects of the different inline citation methods.
The following example shows how it can be coded. It's essentially the same as Harvard referencing, basically replacing parenthesis with <ref> tags.
The Sun is pretty big,<ref>[[#Reference-idMiller2005|Miller 2005]], p.23.</ref>
however the Moon is not so big.<ref>[[#Reference-idSmith2006|Smith 2006]], p.46.</ref>
The Sun is also quite hot.<ref>[[#Reference-idMiller2005|Miller 2005]], p.34.</ref>
== Citations ==
<references/>
== References ==
*{{wikicite|id=idMiller2005|reference=Miller, E (2005). "The Sun", Academic Press.}}
*{{wikicite|id=idSmith2006|reference=Smith, R (2006). "Size of the Moon", Scientific American, 51(78).}}
Result:
The Sun is pretty big, however the Moon is not so big. The Sun is also quite hot.
Citations (short footnote citations + full references example)
- 1. ^ Miller 2005, p. 23.
- 2. ^ Smith 2006, p. 46.
- 3. ^ Miller 2005, p. 34.
References
- Miller, E (2005). "The Sun", Academic Press.
- Smith, R (2006). "Size of the Moon", Scientific American, 51(78).
Note how each full reference is only listed once, but can be be cross-referred to multiple times from the short footnote citations, for example for different page references.
[edit] Section headings for short footnote citations
When footnotes are used solely to support short citations then the section name ==Citations== is recommended. When footnotes have a mix of commentary notes as well as short citations then the section name ==Notes and citations== may be used.[i]
[edit] 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.
[edit] Further reading/External links
An ==External links== or ==Further reading== or ==Books== 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.
[edit] Dealing with citation problems
[edit] Unsourced material
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 biography of a living person, in which case you should request admin assistance. If a particular claim in an article lacks citation and is doubtful, consider placing {{fact}} after the sentence or removing it. If you have time to try and find a reference, please do so; it's better to have 5 fully referenced articles rather than 50 articles all tagged with {{fact}}. It is often just as quick to find and create a reference as it is to tag something with {{fact}}. If you are unsure of how to create references, you may find this tool very useful, as it will create all the necessary reference code from just a few details you supply.
Consider the following in deciding which action to take:
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- If it is doubtful but not harmful to the whole article or to Wikipedia
- Use the {{fact}}, or {{who}} or {{weasel-inline}} tags, but remember to go back and remove the claim if no source is produced within a reasonable time.
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- If it is doubtful and harmful
- 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.
[edit] What to do when a reference link "goes dead"
- See also: Wikipedia:Using the Wayback Machine, WebCite
When a link in the References section or Notes section "goes dead", it should be repaired or replaced if possible, but not 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:
- Some pages can be recovered from the Internet Archive or WebCite. Just go to http://www.archive.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 this was a non-blind citation of 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 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, it is acceptable to drop the link but keep the citation.
- 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, do not remove the inactive reference, but rather record 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 deliberately lags by six months or more. When printed sources become outdated, scholars still routinely cite those works when referenced.
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.
[edit] Convenience links
The term "convenience link" is typically used to indicate a link to a copy of a resource somewhere on the Internet, offered in addition to a formal citation to the same resource in its original format. It is important to ensure that the copy being linked is a true copy of the original, without any comments, emendations, edits or changes. When the "convenience link" is hosted by a site that is considered reliable on its own, this is relatively easy to assume. However, when such a link is hosted on a less reliable site, the linked version should be checked for accuracy against the original, or not linked at all if such verification is not possible.
Where several sites host a copy of the desired resource, the site selected as the convenience link should be the one whose general content is most in line with Wikipedia:Neutral point of view and Wikipedia:Verifiability.
[edit] 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 wikicode for journals, webpages, and other commonly cited sources.
- WP:CITE - Firefox add-in for one-click creation of {{cite news}} information, in footnote format
- 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.
[edit] See also
- Wikipedia:Citation templates - a full listing of various styles for citing all sorts of materials.
- Wikipedia:Verifiability
- Wikipedia:Reliable sources
- 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.
[edit] Notes
i. ^ a b Commentary notes can be shown separately from references or citations - giving a neater appearing alternative compared to having mixed "Notes and references" or "Notes and citations" sections. This is an example of such a note. It isn't generated via the Footnotes method (i.e. via use of <ref> and <references/> tags). Instead it utilizes {{ref}} templates, which give manual control allowing distinct use of (for example) roman numerals instead of automatically allocated ordinal numbers as the identifying notation criteria. This example uses {{ref label}} and {{note label}} variations of the ref templates. The three parameters for this pair of these templates are name, label and id. When id is included in {{note label}} then id is displayed for the note as its back-link (in this example a and b) and its label parameter is not used. Name and id parameters in combination are the matching criteria for link back to and forward from {{ref label}}.
[edit] 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
[edit] Further reading
- Psychology with Style: A Hypertext Writing Guide
- A Guide for Writing Research Papers Based on Modern Language Association (MLA) Documentation
- AMA Citation Style
- Chicago/Turabian Documentation
- Citation Guide - TurabianPDF
- General Guidelines for Citing Government Publications
- Guide to Citation Style Guides
- Sociology style (ASR)
- Uniform Requirements for Manuscripts Submitted to Biomedical Journals
- American Chemical Society reference style guidelines
- Citation Machine
