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Primary, Secondary, and Tertiary Sources

Learn to distinguish primary, secondary and tertiary sources in the humanities and sciences.

What are secondary sources?

Secondary sources are written after the fact. Secondary sources interpret, analyze or expand upon the information contained in a primary source or other secondary source. Many of the scholarly books and articles you may use in class or when completing a research project will cite primary sources.

Like primary sources, secondary sources are often focused on a narrow topic.  However, unlike primary sources, the information contained within a secondary source is not the original material.  For example, the Declaration of Independence would be a primary document.  The book Inventing America: Jefferson's Declaration of Independence by Gary Wills would be a secondary source because Wills analyzes Thomas Jefferson's contributions to the writing of the Declaration of Independence and offers an interpretation of Jefferson's vision. It may cite the Declaration of Independence but only the original Declaration would be primary. Wills' book is secondary because he is not Thomas Jefferson; all he can offer is an interpretation based on what Jefferson wrote.

Use the tabs below to see examples of secondary sources in both the Humanities and the Sciences.


To cite this LibGuide use the following templates:

APA: Northern Essex Community College Library. (Date updated). Title of page. Title of LibGuide. URL

MLA: Northern Essex Community College Library. "Title of Page." Title of LibGuide, Date updated, URL.