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5) Evaluate Sources: Primary, Secondary & Tertiary Sources

A University of Lethbridge Library guide to evaluating sources.


Often, an important step in evaluating any source you intend to use in your research is to determine whether it is a primary, secondary, or tertiary source. You may be given an assignment that requires you to use a particular kind of source; it is thus necessary to know how to identify them. This page defines primary, secondary, and tertiary sources and provides examples of each.

NOTE: Whether a particular source should be considered primary, secondary, or tertiary depends on your research focus. For example, Denis Diderot's Encyclopédie, published in eighteenth-century France, was an encyclopedia, which would generally be categorized as a tertiary source. Scholars today, however, use the Encyclopédie as a primary source to study the ideas and views of Enlightenment thinkers.

Primary Sources

Primary sources provide a firsthand account of an event or activity. They are generated by the people directly involved. They are the original materials on which further research is based. The information in a primary source has not been subject to interpretation, analysis, or evaluation.  Examples of primary sources include:

  • Artifacts (e.g. tools, pottery, coins, furniture, clothing, fossils)
  • Photographs and drawings
  • Works of art (e.g. paintings, plays, literature)
  • Memoirs and autobiographies
  • Books, magazines, and newspaper articles (written by people who have witnessed or participated in the actual event)
  • Patents
  • Empirical data (presented in conference proceedings or journal articles)
  • Interviews
  • Diaries
  • Letters
  • Speeches
  • Government records

Secondary Sources

Secondary sources offer interpretations, analyses, evaluations, or summaries of primary and other secondary sources. They are generally written after the event or activity discussed and are not based on direct observation or involvement in that event or activity. Examples of secondary sources include:

  • Monographs
  • Journal articles (those that do not present new research results)
  • Theses and dissertations
  • Biographies
  • Commentaries and criticisms
  • Magazine and newspaper articles (those that are not based on direct observation or participation)
  • Textbooks (may also be considered tertiary sources)


Tertiary Sources

Rather than reporting or commenting on an event or activity, tertiary sources collect, synthesize, and categorize primary and secondary literature. Examples of tertiary sources include:
  • Encyclopedias
  • Dictionaries
  • Textbooks
  • Almanacs
  • Bibliographies
  • Chronologies
  • Handbooks
Many of these examples are also considered secondary sources, depending on the context.

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Primary vs Secondary Sources