Wikipedia:Identifying and using tertiary sources: Difference between revisions

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{{Essay|interprets=[[Wikipedia:No original research]], and [[Wikipedia:Identifying reliable sources]]|shortcut=WP:TERTIARYUSE|WP:USETERTIARY}}

{{nutshell|1=Analysis and evaluation require reliable secondary sources, and we cannot cite tertiary sources for them. Tertiary sources differ from secondary ones by not themselves providing significant analysis, commentary, or synthesis. However, some tertiary sources are secondary in some applications.}}

Generally speaking, [[tertiary source]]s (for Wikipedia purposes, as discussed at {{section link|Wikipedia:No original research|Primary, secondary and tertiary sources}}, and {{Section link|Wikipedia:Identifying reliable sources|Primary, secondary, and tertiary sources}}) include any compilation of information, without significant new analysis, commentary, or synthesis, from primary and secondary sources, especially when it does not indicate from which sources specific facts were drawn. The distinction between tertiary and [[secondary source]]s is important, because Wikipedia's [[Wikipedia:No original research|no original research]] policy states: "Articles ''may'' make an analytic, evaluative, interpretive, or evaluativesynthetic claim ''{{em|only if''}} that has been published by a reliable secondary source." Thus, such claims cannot be cited to tertiary or [[primary source]]s.

== Identifying ==

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There are many types of {{em|typically}} tertiary sources:

* [[Encyclopedia]]s, [[Dictionary|dictionaries]], [[Encyclopedic dictionary|encyclopedic dictionaries]], and [[Compendium|compendia]], whether general or topical. These are often, but not always, high-quality and reliable sources (compendia are the least likely to be acceptable).

* [[Coffee table book]]s run the gamut from books written by experts and published by internationally renowned museums, to books filled with photographs of a particular place or subject, on down to books whose sole ''raison d'être'' is making people laugh.

* "[[Coffee table book]]s" and [https://www.goodreads.com/list/show/6486.Best_Bathroom_Books "bathroomBathroom books"]. These are usually low-quality sources and presumptivelyshould usually be unreliableavoided.

* School [[textbooks]], especially below the graduate-school level. If they are below the university level, they are treated as categorically unreliable by Wikipedia.

* School [[textbooks]], especially below the university level in the natural sciences and below the graduate-school level in some other fields.

* [[Bibliographies|Bibliographies]] and [[Bibliographic index|indexes]], [[Concordance (publishing)|concordances]], [[Thesaurus|thesauri]], [[database]]s, [[almanac]]s, [[guide book|travel guides]], [[field guide]]s, [[timelines]], and similar works. Quality varies widely.

* [[Abstract (summary)|Abstracts]] of journal articles, legislation, etc., provided by indexing services and specialized search engines (not abstracts written by the article authors themselves). Low-quality sources. May be reliable enough for basics in some cases, depending on reputability of the publisher. The abstract included atop a journal article and written by its own authors is a primary, not tertiary source.

Some of the above kinds of tertiary sources are considered forms of [[secondary literature]] in some disciplines, but {{em|remain tertiary}} (for most of their content) for Wikipedia's purposes including in those disciplines. Not understanding this is a common error by subject-matter experts new to Wikipedia editing.

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The medium is not the message; source evaluation is an evaluation of content, not publication format.

* Sometimes high-quality, generally tertiary individual sources are also primary or secondary sources for some material. Two examples are etymological research that is the original work of a dictionary's staff (primary); and analytical not just regurgitative material in a topical encyclopedia written by a subject-matter expert (secondary).

* Material found in university textbooks ranges from secondary to tertiary, even in the same work, but is most often tertiary, especially at lower levels and covering more basic subjects. Textbooks intended for primary and secondary schools are almost always tertiary and, for Wikipedia purposes, categoricallyreliable only for uncontentious basic unreliablematerial.

* Children's books of any kind are tertiary at best, often primary, and categoricallyare usually unreliable sources. Especially beware citations to books about animals; the majority of them are children's books, so check to be sure. In the same [[Wikipedia:Children's, adult new reader, and large-print sources questionable on reliability|class of suspect works]] are "adult new reader" books, and abridged large-print editions, or any other digest version.

* Some material published in general [[Journalism|news and journalism sources]] (which are [[WP:PRIMARYNEWS|usually secondaryprimary]]) is actually tertiary, such as topical [[overview article]]s that summarize publicly-available information without adding any investigation or analysis; and sidebars of statistics or other [[factoid]]s in an otherwise secondary article. (Some is also primary, such as editorials, op-eds, film reviews, advice columns, and highly subjective investigative journalism pieces.) News reporting is often mostly primary (quoting eyewitness statements, or the observations of an eyewitness reporter, rather than based on more in-depth material from experts and notable organizations). News reporting is treated more and more {{em|as if}} primary, regardless of what it contains, the closer it is to the date of the events, and the further in time those events recede.

* Similarly, not all [[Documentary film|documentaries]] aired on quasi-nonfictional TV networks are actually secondary sources; many are tertiary, and simply summarize various views of and facts about a history or science topic, without the result being novel. Some are even primary, for any exaggeratory conclusions they reach on their own. This has become increasingly true as documentary channels produce more [[WP:FRINGE|fringe]] entertainment material about aliens, ghosts, ancient alleged mysteries, etc.

* [[Systematic review]]s in [[academic journal]]s are secondary sources, especially when they are themselves [[Peer review|peer-reviewed]], despite aggregating information from multiple previous publications. The less analytic kind of academic [[review article]], the [[literature review]], may be secondary or tertiary depending on its content.

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Tertiary online sources that are written in whole or in part by a general-public editing community are [[WP:Identifying reliable sources#User-generated content|user-generated content]], and are not reliable sources. This includes [[content farm]]s, which have a paid but indiscriminate array of innumerable writers, and little editorial oversight, though many of them go to some lengths to disguise their nature.

== Appropriate and inapppropriateinappropriate uses ==

{{shortcut|WP:USETERTIARY}}

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=== Problematic uses ===

{{shortcut||WP:DONTUSETERTIARY|WP:TERTIARYNOT}}

'''Analysis and evaluation:''' A tertiary source cannot be used, as a matter of policy, as a source for "an analytic or evaluative claim". This is left deliberately broad, so it is not subject to [[Wikipedia:Gaming the system|technicality gaming]].

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'''Complex or controversial comparisons:''' Comparative use of tertiary sources can be fraught with problems relating to [[WP:Undue weight|undue weight]], [[WP:Neutral point of view|non-neutral point of view]], [[WP:SYNTH|novel synthesis]], and lack of basic [[WP:Verifiability|accuracy]] if the things being compared are subject to real-world contention, or are complex in nature. For example, a comparison between Christian, Judaic, and Muslim concepts of God is unlikely to produce encyclopedic results if based in whole or part on tertiary sources, which are likely to present a poorly nuanced view of complex theological questions and details of interpretation. Complex comparative work must actually be done in secondary sources cited by Wikipedia for those comparisons. The [[WP:AEIS]] policy does not permit Wikipedians themselves to engage in substantive "analysis, evaluation, interpretation, or synthesis" of facts or sources.

'''Over-inclusive works:''' [[WP:Independent sources#Indiscriminate sources|Indiscriminate sources]] must be considered skeptically when determining both [[WP:Notability|notability]] and [[WP:Undue weight|due weight]]. Unfortunately, a large proportion of tertiary sources are indiscriminate. A guidebook that attempts to describe every restaurant in a city cannot reasonably help establish that a particular restaurant is notable. An index of every paper published about a topic in a given year tells us nothing about the critical reception of any given paper. The more inclusive, comprehensive, even "complete" that a work aims to be, the less useful it is for determining the notability of any subject it mentions. On the up side, the more comprehensive a work is, the more likely Wikipedia editors are to find reliable details in it about any subject within its purview. Thus, in a selection of tertiary sources for a topic, the source that is most reliable for [[WP:Verifiability]] purposes has a tendency to be the least valuable for notability and due weight analysis. The inverse is often not true; an exclusively selective, non-comprehensive source may well be very unreliable, too, simply because it was poorly researched and reflects a superficial, popular-opinion approach to its topic, as is often the case with coffee table books.

'''Better sources available:''' While a good tertiary source can usually be used without incident to source non-controversial facts, such citations can and should be superseded by ones to reliable secondary sources. [[WP:Identifying reliable sources]] tell us: "Each source must be carefully weighed to judge whether it is reliable for the statement being made and is the best such source for that context." It is extremely rare for a tertiary source to be the best such source, for anything, in any context; they're simply often the most readily available and easily digestible (being somewhat predigested). Sometimes a tertiary source can even be replaced with a primary one; for example, a dog breed's actual breed standard (the primary source) is more reliable for the breed's defined characteristics than a tertiary dog breed encyclopedia, though the latter might be very useful for differences and commonalities between varying standards published by different organizations, and may be a good source of additional details, like demographics and breed history. "Stacking" tertiary source citations after a sufficient secondary one [[WP:OVERCITE|is not advised]]; it does not add more verifiability to the claim in the article, but simply adds clutter.

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== See also ==

* [[WP:No original research]] (policy)

* [[WP:VerifiabiltyVerifiability]] (policy)

* [[WP:Identifying reliable sources]] (guideline)

* [[WP:Identifying and using independent sources]] (essay; how to identify when a source may be biased due to a connection to its subject)

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* [[Template:Tertiary source]] (used inside {{tag|ref}})

{{Wikipedia essays}}

[[Category:Wikipedia essays about reliable sources]]