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INAF 180: Science for All

SOURCES: Primary vs. Secondary vs. Tertiary

In the sciences, sources are considered primary, secondary, or tertiary depending on how close they are to what is being studied (i.e., proximity to the original experimental research). See the boxes below for descriptions and examples of each type of source.

Also helpful is the University of Wisconsin-Madison Library's short video below on primary research articles in the sciences:

Primary Sources

-Report the results of experimental research
-Authored by the scientists conducting the experimental research
-Are usually the first appearance of experimental results
-Can comment on or respond to the work of other authors but must still contain substantive original content or experimental research
-Can include informal communication between researchers through email or presented at conferences


  • Research articles in scholarly journals
  • Proceedings of meetings, conferences, and symposia 
  • Dissertations 
  • Technical reports
  • Patents
  • Data sets

Sample:  Nowinski, N., S. Trumbore, E. Schuur, M. Mack, and G. Shaver. 2008. Nutrient Addition Prompts Rapid Destabilization of Organic Matter in an Arctic Tundra Ecosystem. Ecosystems 11:16-25.

Secondary Sources

-Interpret, analyze, evaluate, and/or summarize the information reported by researchers in the primary literature, usually in an attempt to identify trends or draw broader conclusions


  • Review articles*
  • Books
  • Magazine & newspaper articles (may also be primary)
  • Textbooks
  • Data compilations

Sample: Danovaro, R., P. V. R. Snelgrove, and P. Tyler. 2014. Challenging the paradigms of deep-sea ecology. Trends in Ecology & Evolution 29:465-475.

*A review article summarizes the results of several studies or experiments. Its author(s) is not the author(s) of most of the literature reviewed. Review articles appear in journals with titles such as:  

Annual Review of _____
Current Opinion in _____
Nature Reviews
Trends in ____

Tertiary Sources

-Summarize or condense information from primary and secondary sources into a convenient form.


  • Encyclopedias
  • Almanacs

SampleEncyclopedia of Ecology 

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