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PubMed - Searching Medical Literature: Types of Medical Literature

A guide to searching medical literature using PubMed, the MEDLINE search engine from the National Library of Medicine.

Types of Medical Literature

Different types of publications have different characteristics.

Primary Literature
Primary sources are original materials.  It is authored by researchers, contains original research data, and is usually published in a peer-reviewed journal. Primary literature may also include conference papers, pre-prints, or preliminary reports.

Secondary Literature
Secondary literature consists of
interpretations and evaluations that are derived from or refer to the primary source literature. Examples include review articles (specifically meta-analysis and systematic reviews) and reference works. Professionals within each discipline take the primary literature and synthesize, generalize, and integrate new research.

Tertiary Literature
Tertiary literature consists of
a distillation and collection of primary and secondary sources such as textbooks, encyclopedia articles, and guidebooks or handbooks. The purpose of tertiary literature is to provide an overview of key research findings and an introduction to principles and practices within the discipline.


Original research results in journals,
dissertations, conference proceedings, correspondence


Abstracting and indexing services, review articles, systematic reviews, meta-analysis, practice guidelines


Text books, encyclopedias, handbooks, newspapers

Sources: NEJM, JAMA Sources: PubMed, CINAHL, Cochrane Library, Web of Science
Sources:  Goodman & Gilman's, Williams Obstetrics

Adapted from the Information Services Department of the Library of the Health Sciences-Chicago, University of Illinois at Chicago.


Different kinds of information sources are useful depending on your topic and the type of information you need.


Books are good for general background and in-depth coverage of a topic. They are often not as current as journal articles because they take a long time to research, write, and publish.

Books may be useful when:

  • You need a broad overview. There are times when you want someone to explain everything to you - beginning to end. Books are very appropriate for this.
  • Your research topic is historical. Books lend themselves to topics in which the facts don't change much over time.
  • You want several opinions from one place. Some books collect essays that give you several points of view in one source.

Books may not be useful when:

  • The topic is very recent. Books take years to get researched, written, published, purchased, and put on library shelves. If the issue you are researching is constantly changing, a book may be outdated by the time it gets to the library.
  • You have a fairly narrow topic. Sometimes books are too broad-based to address specific or narrow points.


Articles tend to be narrow in scope and are good for focused treatment of a topic. Scholarly journals contain high-quality articles usually written by experts and use data and statistics to back arguments. Popular magazines and newspapers (such as Newsweek, People, or the New York Times) are good for current treatment of a topic and are good resources for editorials and opinions. Note that popular magazines are not peer-reviewed.

Articles may be useful when:

  • Your topic is very recent. Articles are intended to keep people up-to-date on the latest developments in various issues.
  • Your research topic is very narrow in scope. Some topics are so specific, whole books will not be written on them.

Articles may not be useful when:

  • You need background or overview information. Articles tend to focus on a specific aspect of a topic.
  • Your topic covers a long time span. When an issue has a long history, you may only find one aspect discussed in an article.

Web Sites

Web sites can be very good for finding quality information including primary sources, statistical information, educational sites on many levels, policy, opinion of all kinds, and much more. However, you have to take the responsibility to rigorously evaluate each site for quality; anyone can post a Web page, regardless of their expertise or intentions.


Adapted from the University of Connecticut Libraries