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Primary, Secondary & Tertiary Sources

We have access to so many different sources. Let's take a moment to consider what types of evidence they can provide for us based on how closely they witnessed the original event.


When doing research for your courses, you may be asked to use specific types of sources. This guide is designed to highlight the differences between how these classes of sources are created and used.

Click through the blue tabs on the left to access different sections of this research guide.

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Identifying Primary, Secondary and Tertiary Sources

First some definitions

Primary sources 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. 

Secondary sources analyze, review, or summarize information in primary resources or other secondary resources. Even sources presenting facts or descriptions about events are secondary unless they are based on direct participation or observation. Moreover, secondary sources often rely on other secondary sources and standard disciplinary methods to reach results, and they provide the principle sources of analysis about primary sources.

Tertiary sources provide overviews of topics by synthesizing information gathered from other resources. Tertiary resources often provide data in a convenient form or provide information with context by which to interpret it.

While these definitions seem pretty clear, let's look at some examples of sources and consider how time is also a defining factor. See below for more details. 

(Adapted from: VirginaTech Library under CCBY 4.0)

Primary, Secondary & Tertiary Sources (video)

Learn the differences among primary, secondary, and tertiary sources while seeing examples for each type of resource. 

Created by the Suffolk County Community College Library.

Information Cycle

Using Hurricane Katrina from 2005 as an example, this video explains how news, analysis, and scholarly treatments of an event are created and develop over time.

Created by the Polk Library, Univ. of Wisconsin Oshkosh.