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Georgetown Special Collections

Primary Sources

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). Scroll down to 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:


-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 that haven’t been interpreted yet

Sample citation:  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.

*Research articles present original results of a single study or experiment and are divided into sections with headings such as Abstract, Introduction, Materials and Methods, Results (with tables & figures), Discussion, References (Literature Cited). Scientific research articles are usually published in scholarly journals produced by learned societies (e.g., Ecological Society of America) or by commercial publishers (e.g., Elsevier, Wiley, Springer). Researchers submit an article to a journal. It is then refereed by an editorial board of experts in that field before being accepted or rejected for publication.


-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 citation: 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 ____


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


  • Encyclopedias
  • Almanacs

Sample CitationEncyclopedia of Ecology 

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