A tertiary source is an index or textual consolidation of already published primary and secondary sources[1] that does not provide additional interpretations or analysis of the sources.[2][3] Some tertiary sources can be used as an aid to find key (seminal) sources, key terms, general common knowledge[4] and established mainstream science on a topic. The exact definition of tertiary varies by academic field.
Academic research standards generally do not accept tertiary sources such as encyclopedias as citations,[4] although survey articles are frequently cited rather than the original publication.
Overlap with secondary sources
Depending on the topic of research, a scholar may use a bibliography, dictionary, or encyclopedia as either a tertiary or a secondary source.[1] This causes some difficulty in defining many sources as either one type or the other.
In some academic disciplines, the differentiation between a secondary and tertiary source is relative.[1][3]
In the United Nations International Scientific Information System (UNISIST) model, a secondary source is a bibliography, whereas a tertiary source is a synthesis of primary sources.[5]
Types of tertiary sources
As tertiary sources, encyclopedias, dictionaries, some textbooks,[1] and compendia attempt to summarize, collect, and consolidate the source materials into an overview without adding analysis and synthesis of new conclusions.
Indexes, bibliographies, concordances, and databases are aggregates of primary and secondary sources and therefore often considered tertiary sources. They may also serve as a point of access to the full or partial text of primary and secondary sources. Almanacs, travel guides, field guides, and timelines are also examples of tertiary sources.
Wikipedia
Wikipedia is a tertiary source.[6] Because Wikipedia is easily editable by anyone, it is generally not considered to be a reliable source for academic citation.[7] Nevertheless, content on Wikipedia is generally accurate.[8] Wikipedia often proves useful for finding primary and secondary sources.[9]