Subject-specific encyclopedias contain entries focusing on one field of study.
Use an encyclopedia:
Subject dictionaries are more specific than general dictionaries and will define terms associated with specific subjects. Check out these subject dictionaries related to the study of literature and English.
Handbooks are collections of information that provide quick answers in a particular field or about a particular technique.
Wikipedia is not generally considered an appropriate source for academic research.
The credibility of the information is often questioned, as anyone is able to edit the pages.
Wikipedia can, however, be used as a starting point.
Check out the video below for more information: "Using Wikipedia for Academic Research"