Reference resources are a great place to begin your research. They can help you define terms as well as to find basic information about a topic, a chronicle of its history, theories, key people and, frequently, a bibliography of additional recommended sources.
Oxford Bibliographies Online
Provides authoritative research guides helping you to narrow the vast number of citations to the best scholarship on a given topic. Consult, for example:
Oxford Handbooks Online
An outstanding collection of the best handbooks published by Oxford in 14 subject areas, including philosophy. The Handbook series contains in-depth articles that review key issues and major debates.