Tertiary source

A tertiary source is an index or textual consolidation of primary and secondary sources. For example, articles on would be classified as tertiary sources. Some tertiary sources are not to be used for academic research, unless they can also be used as secondary sources, or to find other sources.

Depending on the topic of research, a scholar may use a bibliography, dictionary, or encyclopedia as either a tertiary or a secondary source. This causes difficulty in defining many sources as either one type or the other.

In some academic disciplines the distinction between a secondary and tertiary source is relative.

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.

As tertiary sources, encyclopedias, textbooks, and compendia attempt to summarize and consolidate the source materials into an overview, but may also present subjective commentary and analysis (which are characteristics of secondary sources).

Indexes, bibliographies, concordances, and databases may not provide much textual information, but as aggregates of primary and secondary sources, they are often considered tertiary sources.

Almanacs, travel guides, field guides, and timelines are also examples of tertiary sources.

Survey or overview articles are usually tertiary, though review articles in peer-reviewed academic journals are secondary (not be confused with film, book, etc. reviews, which are primary-source opinions).

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