Please remember that subject-specific reference sources provide background information on topics. They were written by experts in the field and use the terminology or language of that discipline. The bibliographies are valuable because they identify some of the classic research on the topic. These resources may include:
Articles in subject-specific encyclopedias are written by scholars in the field and present an overview of a topic. Not only does the article add to your knowledge of the subject but it may also help you outline your approach to the research (check the subject index at the end of the set, too) and introduce you to more specific aspects of a general, broad topic. The article may also provide you with other keywords that are used to describe your topic. In turn, as you build your vocabulary of keywords for your research topic, you will then incorporate them into your search strategies in the databases. Most articles will have a bibliography to suggest further reading, many times citing the classic research in the field.
Gale Virtual Reference Library is a database that may prove very helpful in identifying definitions for your topics. It is a collection of subject-specific encyclopedias and other background sources that provide a good introduction to a variety of topics.