Before searching, it is helpful to determine what type of information you need. The information available on your topic will depend on the information cycle and the flow of scientific information.

Knowing the package of the information you want (journal articles, books, conference proceedings, reports, etc.) helps determine where you will search.

Flow of Scientific Information

As the diagram indicates:

• an idea first arises in the mind of a researcher or a group of researchers
• the idea is then developed further over a few years of research.
• It is then probably discussed informally in the Invisible College
  • which is the set of colleagues interested in and expert on a particular subject.
  • this kind of informal discussion may occur at seminars, at conferences, through mail or e-mail, or on electronic newsgroups.
• A somewhat more formal stage is reached when the ideas
  • are presented at conferences that do not have published proceedings
• An even more formal stage is when the ideas
  • are published as preprints or technical reports through the author's university department.

  Librarians often refer to this latter sort of publication as grey literature, indicating that it is shadow-like in the sense that it is more difficult to find libraries that have this form of publication than the forms of publication that we see below on the diagram.

The next stage is publication in the primary literature

• either as an article in a journal OR
• as a paper in a published conference proceedings;
• these 2 forms of publication are called the primary literature, since they are the most easily available, yet detailed record of the research.

The next stage is a description of the research in the secondary literature

• for example, abstracts and indexes, or review journals
• which essentially summarizes and points at the primary literature very soon after it has appeared;
• the main purpose of this secondary literature is to facilitate access to scientific information soon after it has been published.

The final stage is a description of the research in the tertiary literature

• which also summarizes and points to the primary literature,
• but generally only after it has become widely accepted and believed.
• examples of tertiary literature include: handbooks, encyclopedias, and textbooks

Note that monographs (also called books) straddle the last two stages. This is because some monographs or books point only to well-accepted scientific research, and other monographs point also to scientific research that is still being evaluated.

from https://libguides.mit.edu/findinfo/flowofinformation