Sources
editResearch that consists of collecting and organizing material from existing sources within the provisions of this and other content policies is, of course, encouraged: this is "source-based research," and it is fundamental to writing an encyclopedia. However, consideration should be given to the kind of source used, to ensure that articles properly represent generally accepted current knowledge about a given topic.
Various professional fields treat the types of sources in differing fashions, but such distinctions are not our concern here. The main focus here is distinguishing between which references articles should principally rely on, and which references have a tendency to be misused for original research. Sources can be divided into two broad categories for these purposes, based upon their quality and reliability: reliable third-party sources and auxiliary sources.
Reliable sources
editAny material that is challenged or likely to be challenged must be supported by a reliable source. "Original research" is a claim for which no reliable source can be found. Producing a reliable published source that advances the same claim taken in context is the only way to disprove original research. If there is a source, but the source or claim is disputed, that is not original research but rather of a question of reliable sourcing or undue weight.
Reliable third-party sources
editReliable third-party sources should be the principle reference material for Wikipedia articles. These sources are up-to-date, written purposefully to inform about the subject they are being cited for, and released by a publisher with a reputation for fact-checking and accuracy. Third-party publications are preferable because they generally provide analysis, offer a more independent view and provide a broader context for the subject. Examples of such references would be recent post-secondary textbooks, or a contemporary work released by a reliable publisher. Peer-reviewed articles in reputable journals are also considered reliable third-party publications. Care should be taken to avoid undue weight and ensure the information cited is used in context.
Using reliable secondary sources
editWhile articles should principally rely on reputable third-party sources, care should still be taken that the claims reported in the article are verifiable in the references cited. Claims should not rely on unclear, incongruent or passing comments, even if the source is generally reliable. Claims left open to interpretation should be precisely cited or avoided. Drawing conclusions not stated in the reference, or extrapolating a position from the claims in a source, is original research regardless of the type of source. Claims based on statements and sections from reliable sources directly dealing with the central topic of the work are preferred. Reporting information from sections that present an extended argument with a conclusion strongly consistent with the argument is encouraged. It is important that reliable references are cited in context and on topic.
Auxiliary sources
editAuxiliary sources should only be used with care, or in context as used in reliable third-party sources. References from questionable, historical and "raw" sources are examples of auxiliary sources. Examples include notable conspiracy theory websites, Bede's Historia ecclesiastica gentis Anglorum and transcripts of the Nixon tapes. A third-party source from one article may be treated as an auxiliary source in another, because the focus has changed. For example, a book by a notable historian is a reliable third-party source for the events it covers, but it would be considered an auxiliary source in the article about the historian. Generally, any source that does not qualify as a reliable third-party source is grouped in this category. The use of these raw, first-hand, or out-of-date sources lends itself to original research, and thus should only be used with caution.
Using auxiliary sources
editArticles should usually rely on reliable third-party sources, but there are some occasions and exceptions when auxiliary sources may prove useful. Article claims that rely on an auxiliary source should (1) only report what the source states, the accuracy of which is easily verifiable by any reasonable, educated person without specialist knowledge, and (2) make no analytic, synthetic, interpretive, explanatory, or evaluative claims. Contributors drawing on auxiliary sources should be careful to comply with both conditions. Of course, auxiliary sources may be used freely as they are used in reliable publications. In that instance, an editor would be relying on a reliable third-party reference to present, analyze and/or interpret an auxiliary source.
Reliable auxiliary sources
editSome of these sources may be particularly reliable and helpful in presenting a complete encyclopedic article, such as census data. Some auxiliary references may also be useful for providing supporting facts, figures or limited quotations to accompany claims and analysis from reliable secondary sources. However, serious care should be taken to avoid presenting a claim or interpretation, explicit or implied, differing from the reliable references cited. Editors should use discretion and consensus to identify such circumstances.
Auxiliary sources may also prove useful for topics in which they are a self-reference, or a primary source. Self-published and dubious sources are permitted in articles about themselves, as are other auxiliary sources. For example, the subject's own works are suitable sources for his/her beliefs in biographical articles. In religious articles, a movement's internal commentaries (such as a catechism) are suitable sources for its beliefs, but its religious scriptures are not (since sacred texts often have variable and abstract interpretations).