Wikipedia:No original research/PSTS

= Primary, secondary and tertiary sources =

Wikipedia articles should be based on reliable, published secondary sources and, to a lesser extent, on tertiary sources and primary sources. Secondary or tertiary sources are needed to establish the topic's notability and avoid novel interpretations of primary sources. All analyses and interpretive or synthetic claims about primary sources must be referenced to a secondary or tertiary source and must not be an 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 appropriate in any given instance is a matter of good editorial judgment and common sense, and should be discussed on article talk pages. A source may be considered primary for one statement but secondary for a different one. Even a given source can contain both primary and secondary source material for one particular statement. For the purposes of this policy, primary, secondary and tertiary sources are defined as follows:


 * Primary sources are original materials that are close to an event, and are often accounts written by people who are directly involved. They offer an insider's view of an event, a period of history, a work of art, a political decision, and so on. Primary sources may or may not be independent sources. An account of a traffic incident written by a witness is a primary source of information about the event; similarly, a scientific paper documenting a new experiment conducted by the author is a primary source for the outcome of that experiment. Historical documents such as diaries are primary sources.
 * : Unless restricted by another policy,
 * Primary sources that have been reputably published may be used in Wikipedia, but only with care, because it is easy to misuse them.
 * Any interpretation of primary source material requires a reliable secondary source for that interpretation.
 * A primary source may be used on Wikipedia only to make straightforward, descriptive statements of facts that can be verified by any educated person with access to the primary source but without further, specialized knowledge. For example, an article about a musician may cite discographies and track listings published by the record label, and an article about a novel may cite passages to describe the plot, but any interpretation needs a secondary source.
 * analyze, evaluate, interpret, or synthesize material found in a primary source yourself; instead, refer to reliable secondary sources that do so.
 * base an entire article on primary sources, and be cautious about basing large passages on them.
 * add unsourced material from your personal experience, because that would make Wikipedia a primary source of that material. Use extra caution when handling primary sources about living people; see, which is policy.


 * A secondary source provides an author's own thinking based on primary sources, generally at least one step removed from an event. It contains an author's of the facts, evidence, concepts, and ideas taken from primary sources. Secondary sources are not necessarily independent sources. They rely on primary sources for their material, making analytic or evaluative claims about them. For example, a review article that analyzes research papers in a field is a secondary source for the research. Whether a source is primary or secondary depends on context. A book by a military historian about the Second World War might be a secondary source about the war, but where it includes details of the author's own war experiences, it would be a primary source about those experiences. A book review too can be an opinion, summary, or scholarly review.
 * : Wikipedia articles usually rely on material from reliable secondary sources. Articles may make an analytic, evaluative, interpretive, or synthetic claim that has been published by a reliable secondary source.


 * Tertiary sources are publications such as encyclopedias and other compendia that summarize, and often quote, primary and secondary sources. Wikipedia is considered to be a tertiary source. Many introductory undergraduate-level textbooks are regarded as tertiary sources because they sum up multiple secondary sources.
 * : Reliable tertiary sources can help provide broad summaries of topics that involve many primary and secondary sources and may help evaluate due weight, especially when primary or secondary sources contradict each other. Some tertiary sources are more reliable than others. Within any given tertiary source, some entries may be more reliable than others. Wikipedia articles may not be used as tertiary sources in other Wikipedia articles, but are sometimes used as primary sources in articles about Wikipedia itself (see Category:Wikipedia and Category:WikiProject Wikipedia articles).