Reference sources serve three main functions:

1. Provide background information on, or broad overviews of, a subject (encyclopedias). Wikipedia is an encyclopedia. The best encyclopedias have signed entries (by recognized experts) along with recommendations, from that expert, for further reading on the subject. See for example the article on the the student protest at Kent State University in the St. James Encyclopedia of Popular Culture.
2. Compile factual information (chronologies and statistical compendia).
3. List primary and secondary sources on a subject (bibliographies).

Encyclopedias attempt to summarize the state of knowledge in a field of inquiry. Encyclopedias are sometimes called tertiary sources because they summarize the secondary literature on a topic. An encyclopedia can be a valuable starting point for your research.

Three online reference collections that students often find useful are:

Some specific encyclopedias you might find helpful:

Bibliographies (sometimes called "handbooks" or "guides") can assist you in charting a path through the vast amount of research available on a topic. Specialized bibliographies can also help you identify difficult-to-find materials.

Recommended online sources for biographical information:

Additional biographical encyclopedias:

In addition to biographical encyclopedias, biography indexes can help you find biographies published in sources other than encyclopedias (magazine articles, books):