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What is a Tertiary Source – Complete Guide With Examples

Published by at August 22nd, 2023 , Revised On August 22, 2023

When diving deep into research, understanding the nature and origin of your sources becomes indispensable. In the vast ocean of information, sources are typically categorised into three types: primary, secondary source, and tertiary.

In this blog, we will discuss tertiary sources. 

What is a Tertiary Source?

A tertiary source is an information source that compiles, analyses, and synthesises both primary and secondary sources. Tertiary sources provide an overview or summary of a topic, making complex information more accessible and manageable due to our natural cognitive bias to simplify. They are one step removed from the event or phenomenon under study since they are based on secondary sources (which are based on primary sources).

To put it in simple terms, if you were to define a tertiary source, it can be considered as the third-hand account or representation of events or information. However, be mindful of the actor-observer bias; how we perceive an event might differ from how it is represented in the source.

Examples of Tertiary Sources

Here are a few examples of tertiary sources. 


Both general ones, like the Encyclopedia Britannica, and specialised ones, such as the Encyclopedia of World History.


These list primary and secondary sources on a particular topic. For instance, a bibliography on Shakespeare might list all the primary works (his plays and poems) and important secondary analyses (articles and books that interpret his works).


General and specialised dictionaries that provide definitions or explanations of terms and concepts.


Lists of people, organisations, or institutions, usually with contact information.


Contain statistical, factual, and current information. This source evaluation method can be efficient for quick reference.

Fact Books or Handbooks

Such as a handbook on birds or a fact book about countries.


The “Periodicals Index” lists articles from various journals and magazines and could sometimes demonstrate publication bias if certain topics are favoured.


Such as museum guides, how-to guides, and style manuals.


Brief summaries of articles or reports. This could be where the ceiling effect might influence how much information gets condensed.

Atlases and Maps

Some maps can be primary or secondary, but many atlases compile various maps and related data, making them tertiary.

Course Textbooks

These often synthesise primary and secondary material to give students an overview of a subject. Though, be wary of the Pygmalion effect, where expectations can influence outcomes or perceptions.


Such as JSTOR or ProQuest provide access to numerous primary and secondary sources but can be considered tertiary because of their role in organising and categorising knowledge.

Review Articles

Articles in scientific journals or magazines that summarise the current state of research on a topic. However, one must be careful of confirmation bias when reading reviews that align closely with their pre-existing beliefs.

Chronologies or Timelines

Lists of events in chronological order.

Biographical Works

Such as “Who’s Who” provides brief details about various people. It is crucial to ensure that there is not any explicit bias in these details, which can often cloud the true essence of an individual’s achievements or personality.

How to Tell If a Source is Tertiary

A tertiary source provides overviews, summaries, or generalisations of primary and secondary sources. Tertiary sources are often intended for a general audience and are designed to simplify finding and integrating primary and secondary source material. Here are ways to identify if a source is tertiary:


Tertiary sources are typically used to organise, index, or summarise data and information. If the main intent of the source is to provide an overview or compilation of other sources, it’s likely tertiary.


These sources often summarise or compile the work of others. They might provide broad overviews, general information, or synthesised data.


  • Encyclopedias (e.g., Encyclopedia Britannica, World Book)
  • Directories
  • Fact books
  • Manuals
  • Guidebooks
  • Bibliographies (lists of sources on a specific topic)
  • Databases that offer summaries
  • Textbooks (though some might argue they sit between secondary and tertiary)
  • Almanacs
  • Handbooks


Tertiary sources may not always provide original data or detailed citations, as their primary goal is summarisation. It could be a tertiary source if a source only provides a general overview without deep citations or references.

Detail Level

Tertiary sources do not typically dive deep into nuanced analysis or detailed topic examination. Instead, they provide a high-level overview or summary.


Experts might write tertiary sources but do not necessarily represent original research or new interpretations by those experts. They compile and summarise what’s already known.

Publication Source

Reputable academic presses might publish tertiary sources, but they are just as often produced by commercial publishers or other entities more focused on wide distribution to the public rather than contributing to scholarly discourse.


If the primary audience for the source seems to be the public or those new to a subject, it might be a tertiary source.

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How and When to Use Tertiary Sources

Here is how and when to use tertiary sources. 

How to Use Tertiary Sources

Starting Research

At the beginning of any research project, tertiary sources can help you get a broad overview of your topic. They can help identify the key themes, trends, names, dates, and other foundational information.

Identifying Primary and Secondary Sources

Tertiary sources often point to primary and secondary sources on a given topic. For example, a bibliography might list all the major works on a specific topic.

Quick Facts and Figures

If you need a quick fact, date, or another specific piece of information, tertiary sources like almanacks or fact books can be invaluable.

Understanding Context

Some tertiary sources, like historical timelines, can help you understand the broader context in which an event occurred.

Comparative Analysis

Some tertiary sources can help compare theories, methodologies, or views on a topic.

When to Use Tertiary Sources:

Preliminary Research

Before diving deep into a subject, use tertiary sources to familiarise yourself with the main ideas and events.

When Primary or Secondary Sources are Scarce

If primary or secondary sources are difficult to find or inaccessible, tertiary sources might offer summaries or overviews that can be useful.

Filling Knowledge Gaps

If there are gaps in your understanding or knowledge of a subject, tertiary sources can help fill those gaps.

Reference and Verification

To double-check a date, name, or fact, tertiary sources can be a quick and reliable tool.


  • Tertiary sources generally provide a broad overview rather than an in-depth analysis. They should not be solely relied upon for comprehensive research.
  • While tertiary sources aim to be objective, they can sometimes carry affinity bias or contain outdated information, especially if they are not regularly updated. Also, there’s often a bias for action; we might be inclined to trust and act on tertiary sources because they are more accessible, but they always ensure accuracy. Scholarly source recommendations emphasise verifying information using other sources when accuracy is critical.
  • While tertiary sources are great starting points, scholarly and comprehensive research typically requires primary and secondary sources to provide evidence, detail, and depth.

Frequently Asked Questions

A tertiary source consolidates and summarises information from primary and secondary sources. Examples include encyclopedias, almanacs, and textbooks. They provide overviews on topics, making them useful for general understanding but not for in-depth research.

An example of a tertiary source is an encyclopedia. Encyclopedias provide summarised and consolidated information on a wide range of topics, drawing from primary and secondary sources. They offer general overviews and background knowledge rather than detailed or original research insights.

Yes, Lexicomp is a tertiary source. It is a clinical drug information resource that provides comprehensive drug monographs, drug interaction tools, and other drug-related information. Lexicomp consolidates and summarises data from primary and secondary sources, offering healthcare professionals quick access to medication and patient care information.

Primary sources originate from the time or event studied, offering first-hand accounts like diaries or raw data. Secondary sources analyse, interpret, or critique primary sources, like scholarly articles. Tertiary sources consolidate and summarise, such as encyclopedias. Identifying involves assessing the content’s proximity to the original event or data.

In research, a tertiary source consolidates and summarises information from primary and secondary sources. It provides overviews and general knowledge rather than original content or detailed analysis. Examples include encyclopedias, textbooks, and handbooks. They’re useful for background information but aren’t typically cited in scholarly research.

Tertiary sources of information consolidate and summarise content from primary and secondary sources. They provide general overviews and are not original or analytical. Examples include encyclopedias, textbooks, handbooks, and directories. These sources are helpful for obtaining background knowledge but are rarely cited in academic research.

No, newspapers are typically considered primary sources because they provide first-hand accounts of events shortly after they occur. However, in some contexts, if a newspaper article reviews or summarises past events or other sources, it could function as a secondary source. They aren’t typically classified as tertiary sources.

Movies can be primary, secondary, or tertiary sources, depending on their content and use. A film capturing real-time events is primary. If analysing or interpreting a historical event, it’s secondary. Tertiary usage is rare, but if a film summarises or compiles other sources, it could be considered tertiary— context matters.

Yes, encyclopedias are considered tertiary sources. They consolidate and summarise information from both primary and secondary sources, providing general overviews on various topics. Encyclopedias are used for obtaining background knowledge and are not typically relied upon for in-depth scholarly research or original insights.

Books can be primary, secondary, or tertiary sources, depending on their content. Autobiographies or first-hand accounts are primary. Most academic books analysing a topic are secondary. Handbooks, dictionaries, and encyclopedias, which summarise and compile information, are tertiary. The classification depends on the book’s relationship to the subject.

Articles can be primary, secondary, or tertiary sources, depending on their content. Research articles presenting original data are primary. Review articles summarising multiple studies are secondary. Summaries or overviews found in reference databases or basic introductory pieces can be tertiary. The classification hinges on the article’s content and purpose.

About Owen Ingram

Avatar for Owen IngramIngram is a dissertation specialist. He has a master's degree in data sciences. His research work aims to compare the various types of research methods used among academicians and researchers.