Most reference resources are considered "tertiary" souce materials. These books and websites provide background information and an overview and analysis of a subject or concept.
Tertiary souirces have been compiled from secondary sources. Unlike a secondary source book or journal article, tertiary sources are not intended to be read in their entirety. Instead, they are most often used to clarify terms and concepts about a particular topic. Tertiary sources include:
- Almanacs and Factbooks
- Bibliographies*
- Chronologies
- Dictionaries and Encyclopedias*
- Directories
- Guidebooks
- Indexes and Abstracts
- Manuals
- Textbooks*
*Also considered secondary
[Image Source: Il Gazzettiere Americano contenente un distinto ragguaglio di tutte parti del Nuovo mondo . . . (Livorno, 1763), vol. 2, p. 111 (first Italian edition of the American Gazetteer [London, 1762]). (Special Collections Department, University of Virginia Library)]