Wikipedia:Handling primary, secondary and tertiary sources (proposed guideline)

Primary, secondary and tertiary sources may all be used in Wikipedia. Care must be taken to avoid original research by editors, to avoid giving undue weight to particular observations, views or experiences, and to establish the notability of topics covered by Wikipedia. Wikipedia articles should rely on published secondary sources and, to a lesser extent, on tertiary sources. In theory, primary sources may also be used. Reliance on primary sources can lead to interpretive clambs, analyses, or synthetic claims, which must be referenced to a specific source that makes the same claim or analysis. It is not proper to rely on original analysis of the primary-source material by Wikipedia editors.

Appropriate sourcing can be a complicated issue, and these are general rules. Deciding whether primary, secondary or tertiary sources are more suitable on any given occasion is a matter of common sense and good editorial judgment, and should be discussed on article talk pages. The policies that deal with sourcing are Verifiability and No original research; this section of the latter deals with primary, secondary, and tertiary sources. In the event of inconsistency between the policies and this page, the policies take priority, and this page should be updated to reflect them.

Categorising as primary, secondary or tertiary
For the purposes of Wikipedia policies and guidelines, primary, secondary and tertiary sources are defined as follows:


 * Primary sources are very close to an event, often accounts written by people who are directly involved, offering an insider's view of an event, a period of history, a work of art, a political decision, and so on. An account of a traffic accident written by a witness is a primary source of information about the accident. Historical documents such as diaries are primary sources.


 * Secondary sources are at least one step removed from an event. They rely for their material on primary sources, often making analytic, synthetic, interpretive, explanatory, or evaluative claims.  Secondary sources include books, newspaper reports, reviews of films etc. and many academic papers, although this always depends on the context. For the purposes of Wikipedia, some publications, including many scientific papers, are partly a primary source and partly secondary.


 * Tertiary sources are publications such as encyclopedias or other compendia that mainly summarize secondary sources. Wikipedia is a tertiary source. Many introductory undergraduate-level textbooks are regarded as tertiary sources because they sum up multiple secondary sources.

Context
Whether a source is primary, secondary or tertiary can depend on the topic that an article is covering. For example, the summary for policy makers from the IPCC is a secondary source for the article Global warming but it would be a primary source if used for the article Intergovernmental Panel on Climate Change. Similarly, a book review in a newspaper is a secondary source on the book and its author but a primary source on the newspaper and the reviewer.

A newspaper report is normally considered to be a secondary source, since it will report more than has been witnessed by the journalist directly and the journalist will apply some judgment to the use of sources. However, historians often consider an old newspaper report to be a primary source, since it is much closer to the event than they are.

For an article about a work of fiction, the only primary source is the work itself. Comments on the work by its author are secondary (but not independent) sources.

Complex source categorisation
Some sources can not be categorised as entirely primary, secondary or tertiary. A published edition or translation of a primary source, such as Newton's Principia or the Letters of Abelard and Heloise, is itself a primary source. However, the notes or commentary to that edition or translation, which present the editor's or translator's interpretation of the text, are secondary sources. Similarly, a commentary or a "behind the scenes" documentary is a secondary source on a motion picture, even if they are on the same DVD.

In the sciences, original contributions which disclose new data or ideas, and thereby establish priority of discovery, are called primary publications or primary literature. A primary publication may include new experimental data and results, for which it is clearly a primary source. It may include analysis and summary of previous work, which is clearly a secondary source on that work. It may include analysis and interpretation of the new results, which is more of a grey area. This part of the work analyses and interprets the experimental data, which implies that it is secondary, but it is still the work of the original author and may lack a wider perspective, which implies that it is primary.

Grey areas
Sometimes it is difficult to decide if a particular source is primary or secondary. Maybe you are pretty sure that it is primary but someone else is arguing that it is secondary. On these occasions, it is best to this is a guideline on how to apply other policies and guidelines, most importantly the policy no original research and the guideline on notability. Do not worry too much if the source is primary or secondary.

If the issue is notability, look at the general notability guideline and any area-specific guidelines such as WP:Notability (books). In the case of the general notability guideline, although it mentions secondary sources as part of the explanation, it more prominently states that sources should be independent of the subject. Think about whether the source is independent of the subject.

If the issue is original research, it is possible to create original research based on any source: primary, secondary or tertiary. Think about what original research means in Wikipedia and whether the addition being proposed is actually original research.

Original research
It is possible to create original research based on any source: primary, secondary or tertiary; and in all cases this should be avoided. However, particular care should be taken with primary sources because it is easy to misuse them. Most statements of fact or opinion come ultimately from primary sources, via analysis, interpretation or synthesis. When these statements are made in Wikipedia, they should be cited to a source that states the same facts or opinions, rather than relying on original analysis, interpretation or synthesis of primary or other sources by Wikipedia editors. Where no reliable source can be found for such a citation, the statement is original research and should not be made in Wikipedia.

Original research does not include describing the contents of a primary source in a way that can be verified by a reasonable, educated person without specialist knowledge.

Unsourced material obtained from a Wikipedian's personal experience, such as an unpublished eyewitness account, should not be added to articles. It would violate the policies on both original research and verifiability, and would cause Wikipedia to become a primary source for that material.

Undue weight
Primary sources often have a very narrow perspective. Using primary sources can give undue weight to particular observations or the views and experiences of the author of the primary source. It can also give undue weight to the views and experiences of an editor who selects specific statements from a body of primary sources for inclusion in an article. Secondary sources often have a wider perspective since they will analyse many primary sources or seek to put a single primary source into a wider context.

Particular examples of this, in scientific publishing, are synthesis reports and meta-analyses. These secondary publications are designed to take many primary publications into account, giving each piece of evidence an appropriate weight.

Quoting primary sources
Quoting from a primary source is often problematic. It is easy to quote primary sources selectively, out of context, or in other ways that are inappropriate and constitute original research or give undue weight to a particular viewpoint. In contentious cases, providing a citation of a high-quality secondary source that quotes the primary source in the same way is essential to show that an article is not giving the selected quote undue weight. If no such secondary sources can be found, this is an indication that the article contains original research and undue weight problems that need to be addressed.

When citing a secondary source quoting a primary source, it is good practice is to verify that the secondary source is quoting the primary source correctly, and to add an ancillary citation to the primary source itself. If you can not find the original primary source, do not cite it. i.e. if you have seen only the secondary source, your citation should be of the form If you have seen both sources, your citations should be of the form
 * 1) Source A, quoted in Source B.
 * 1) Source A, quoted in Source B.
 * 2) Source A.

For large sources, allow the quoted section to be found by providing page numbers or similar information. Do not include the full text of lengthy primary sources in Wikipedia; but if such a source is out of copyright, it may be appropriate to include it in Wikisource.

Notability
A primary source on a topic can not establish the topic's notability. For example, a book can not establish the notability of itself or its author. The general guideline is that if a topic has received significant coverage in reliable sources that are independent of the subject, it is presumed to satisfy the inclusion criteria for a stand-alone article. Such independent sources will be secondary or tertiary.

N.B. Being secondary or tertiary is not a guarantee of independence. See the essays Independent sources and Third party sources for the views of some Wikipedia editors on this subject.

Wikipedia as a source
Wikipedia, as an encyclopedia, is a tertiary source. However, Wikipedia and sources that mirror or source information from Wikipedia may not be used as secondary or tertiary sources. Wikipedia articles are sometimes used as primary sources in articles about Wikipedia.