Be aware that information vary in terms of coverage of a topic. Note whether an information source adds to other information you have used or gathered.

A good way to get an overview of the coverage of an information source is by browsing the material. Check the table of contents, index, or abstract/summary, if available.

Ask yourself the following:

How extensively does the information source cover your topic in terms of time?

How extensively does the information source cover your topic in terms of geography?

How extensively does the information source cover your topic in terms of specificity?

How extensively does the information source cover your topic in terms of point of view?

Is the information complete or abridged?

Also consider the following questions for web sites:

Is access to the information restricted or limited?