Encyclopedias attempt to summarize the state of knowledge in a given field of inquiry. That field of inquiry is usually defined in the title. For example, the Encyclopedia of the Mexican American War summarizes what is known about this conflict (as of the date of the encyclopedia's publication!). Encyclopedias not only give you the broad overview of the field, but they often recommend sources (usually secondary sources, but sometimes also primary sources) to consult for further research.
A very extensive collection of useful reference works published by Gale and affiliated publishers, including general and subject-specific encyclopedias. Gale is a major publisher of encyclopedias and other reference sources.
Large collection of encyclopedias and dictionaries. It includes some important reference works in History, Philosophy, Religious Studies, and related fields. Works tend to feature shorter entries, with exceptions.
Encyclopedias for Researching Latin American History to Independence