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Research Guide: Primary vs Secondary vs Tertiary Sources

This guide introduces new researchers to how to plan their search for information.

Where can I find primary sources

The library provides access to many scholarly articles containing original research. These can be found on our Find An Article page.

Additionally, many secondary sources will reference primary sources. If we do not have the book or article you are looking for, you can request it through our online form.

The Library of Congress also maintains an extensive online collection of primary sources from American History, covering a variety of topics, including arts, politics, science, sports, and more!

Are primary sources scholarly?

Some scholarly resources are primary and some are secondary. If an article talks about the authors original research, then it is primary. If a scholarly resource instead reviews or analyzes an event or the works of another author, then the work is secondary.

What is a primary source?

A primary source is a document or item that contains firsthand accounts of an event or original research on a topic. These can include any of the following:

  • diaries
  • letters
  • newspaper articles
  • scholarly research articles
  • photographs/films
  • speeches
  • autobiographies


On the other hand, secondary sources are analysis or restatements of events that the author was not directly involved in. These can include:

  • most books about a topic (including textbooks)
  • articles that analyze and use research performed by other scholars


Tertiary sources are compilations of information from primary and secondary sources and are used to either provide an overview of a topic or help users to find more resources related to the topic. These typically include:

  • Dictionaries and encyclopedias
  • Bibliographies and indexes

When to use which?

Primary sources are useful when you want a view of what people saw and how they reacted at the time of an event.


Secondary sources often have a more complete view as more information has been found after the fact. Use them when you are looking for in-depth analysis.


Tertiary sources are used when you are looking for a quick overview or need to know where to find more information on a topic.

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