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Primary, Secondary, and Tertiary Sources


Research usually starts with a quick Google search and looking at the first few hits, but beware: not all sources are the same. Understanding the difference between primary, secondary and tertiary sources is a critical step in writing a grade-A paper.

Each source type provides information that will support your research paper. In fact, they are all related; one cannot be built without the other. Below we describe what each source is and how it can help you research and write a better paper.

As you find your primary, secondary, and tertiary sources, cite them all at CitationMachine.com! Select APA format, MLA format, Chicago Manual of Style, or any one of our thousands of citations style.

Primary sources

In a world of copies, the primary source is the original. It is the eyewitness interview, the video tape, the speech, art work, study, or statistical data. Keep in mind, primary sources are first hand accounts, but they are not perfect. They are subject to the biases of their creators and the particular time period they were created in. In a publication cycle, primary sources come first, which is how they got their name.  


Primary sources lend an argument color, weight, and perspective. Primary sources are building blocks that allow the author to create new theories.


Basing an entire paper on a single primary source makes your argument easy to attack. Even video tapes can be interpreted from may different perspectives. When using primary sources, more than one should be consulted.

Primary source examples:

Letters, emails, photographs, interviews, video and audio recordings, eyewitness accounts, works of art, experiment results, statistics, blog posts legal documents (i.e., birth certificates, marriage licenses, and adoption records), etc.

Real-world example:

If you were writing about the Great Chicago Fire of 1871, photographs, and eyewitness accounts would be great primary sources.

Secondary sources

Secondary sources are built from primary sources and they come second in the publication cycle. A secondary source, like a newspaper article or book uses primary sources to present a particular idea. Secondary sources are organized like a story with a beginning middle and end.


Secondary sources are easy to find and access. They can also be a great resource for finding primary sources that support your paper (check out their bibliographies or parenthetical citations).


Secondary sources can distract you from your own point of view because they already present a well-supported argument. Relying too heavily on secondary sources can easily lead to accidental plagiarism. It is best to review primary sources after you have establish your own point of view.

Secondary source examples:

Magazine and newspaper articles, scholarly journal articles, movie reviews, book reviews, etc.

Real-world example:

Newspaper articles written at the time of the Great Chicago Fire.

Tertiary sources

Tertiary sources, like guidebooks, are the least original of the bunch. They come third in the publication cycle and are usually a list or summary of many secondary sources.


Tertiary sources are a great place to begin research and decide where you would like to study further. They provide a global understanding of your subject and highlight important facts and figures that should be included.


Tertiary sources often lack the firsthand knowledge and color given by primary sources. They are also missing the elements of good storytelling that make secondary sources interesting to read.

Tertiary source examples:

Wikipedia, encyclopedias, dictionaries, almanacs, guidebooks, manuals, handbooks, etc.

Real-world example:

An encyclopedia or wikipedia article about the great Chicago Fire.


Text and reference books can be categorized as tertiary sources when they list or summarize rather than present original information.

As you can see, each source-type can play a role in creating a great paper. How you use them to write an interesting and balanced paper is up to you.

Once your paper is done and full of great sources, why not run it through a Citation Machine Plus paper check? It’ll help you spot potential issues with spelling, subject-verb agreement, proper noun capitalization, word choice, and more!

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