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Wikipedia
Encyclopedias and Other Reference Sources in the Age of the Web
Tertiary sourcespresent summaries or condensed versions of materials, usually with references back to the primary and/or secondary sources. They can be a good place to look up facts or get a general overview of a subject, but they rarely contain original material.
Secondary sourcescontain commentary on or discussion about primary sources. The most important feature of secondary sources is that they offer an interpretation of information gathered from primary sources.
Primary sourcesare original documents containing first-hand information about a topic. They allow researchers to get as close as possible to original ideas, events, and empirical research as possible. Such sources may include creative works, first hand or contemporary accounts of events, and the publication of the results of empirical observations or research.
Examples: Diaries, Interviews, Historical documents, Original Art, Photographs, Audio/Video recordings, works of literature
Source: Virginia Tech Libraries. (2011, August 2). Primary, secondary, and tertiary sources. Retrieved October 18, 2016, from Virginia Tech University Libraries, http://www.lib.vt.edu/help/research/primary-secondary-tertiary.html
