Specialized reference sources--like dictionaries and subject encyclopedias, provide overviews of topics and descriptions of concepts and ideas. They can also provide definitions, statistics, and other details. You can use this type of source to help narrow your research topic, find data to support your thesis, and identify keywords and main ideas to use as search terms.
The sources mentioned here normally also include bibliographies written by experts, which can provide a direct introduction to the scholarly literature in a field of study.
Online Encyclopedias and Dictionaries:
Specific Topics in Philosophy: