Tertiary Sources — Guide with Examples

02.03.23 Types of sources Time to read: 4min

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As a student, you must understand the different research sources you will find for citing your academic papers. Apart from primary and secondary sources, tertiary sources are helpful and make your research easier. This guide discusses what tertiary sources are, when to use them, and how to identify them while offering some examples.

Tertiary Sources – In a Nutshell

There are three categories of research sources1: primary, secondary, and tertiary. A tertiary source offers oversight of information contained in primary and secondary sources without original analyses or interpretations.

Some common tertiary sources include:
• Bibliographies and indexes
• Encyclopaedias and dictionaries
• Guidebooks, manuals, almanacs, and directories
• Databases
• Textbooks

Definition: Tertiary sources

Tertiary sources help students and researchers collect, index, organise, and compile secondary and primary sources2. They list the other types of sources and give background information on various topics, e.g., how dictionaries and databases do. You may use a tertiary source to understand a topic better, but you cannot use it as a citation.

In an academic paper, you should mainly use secondary and primary sources since they offer information on which you can base your thoughts and ideas. Remember that the rules for choosing sources and citing them vary greatly depending on your study field, so clarify this with your professor when in doubt.

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How to identify tertiary sources

Tertiary sources do not offer original insights or analyses like primary or secondary sources3. However, a tertiary source may depend on your research question and how you use this source.

For instance, encyclopedias are mainly considered tertiary sources. However, a research study focusing on developing comprehensive writing may use encyclopaedias entries as evidence, making them a primary source.

Ask the following questions to identify which source is tertiary:

  • Are you using the source to gain background information or analyse the source itself?
  • Does the source summarise information from other sources? (Tertiary source)
  • Does the source offer original content? (Primary source)
  • Does the source evaluate other sources? (Secondary source)

Examples of tertiary sources

Tertiary sources offer a wide range of relevant information, including broad overviews, key terms, lists of reliable sources, and definitions. You can find many sources offline (in your local library or bookshop), including in textbooks and directories. Some reliable online sources include guidebooks and indexes.

Here is how these sources help:

  • Manuals, textbooks, dictionaries, and encyclopaedias: These sources define and give overviews of topics based on secondary and primary sources.
  • Timelines, databases, directories, bibliographies, and indexes: These offer little textual insight but organise crucial information and help you locate primary and secondary sources.

When to use tertiary sources

Although tertiary sources can be credible, you cannot attribute them to a single author, and they lack the specialised knowledge expected in scholarly sources. Therefore, you cannot cite them in your research paper.

However, you can still use these sources in the early stages of your research process4 to:

  • Identify key scholars
  • Establish background information
  • Understand emerging debates in your study field
  • Identify relevant terms and keywords


Most universities do not accept tertiary sources mainly because they are not credible enough. Although you can use these sources during early research, you cannot base your writing on them or cite them.

Since these sources summarise both secondary and primary sources, incorporating them during research enables you to lay a strong foundation and makes the entire writing process less time-consuming.

Tertiary sources show an overview of a topic and rarely cite other materials. Therefore, such a source does not show opinions or biases toward a topic.

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1 University of Wisconsin-Green Bay. “Research Guides: Types of Sources: Types of Sources.”. Accessed February 2, 2023. https://libguides.uwgb.edu/sourcetypes.

2New York University. “Research Guides: Primary Sources: Primary Sources.” Accessed February 2, 2023. https://guides.nyu.edu/primary/primary-sources/primary-sources#:~:text=A%20primary%20source%20%28also%20called%20original%20source%29%20is,an%20original%20source%20of%20information%20about%20the%20topic.

3 Walden University. “Academic Guides: Citations: Secondary Sources.” Accessed February 2, 2023. https://academicguides.waldenu.edu/writingcenter/apa/citations/secondarysources#:~:text=Secondary%20sources%20refer%20to%20sources%20that%20report%20on,as%20these%20citations%20are%20kept%20to%20a%20minimum.

4 Researchwriting. “Overview of Research Process.” Accessed February 2, 2023. https://researchwriting.unl.edu/overview-research-process.