The academic subject encyclopedias and handbooks listed here are useful for:
They are edited, curated sources of authoritative information.
Wikipedia can also be a good launch-pad for your research, providing background and suggesting sources. Be sure to actively fact check: compare your facts (especially facts from any wiki-based source) with other sources.
Use the "search within this book" feature:
Wiley-Blackwell Encyclopedia of Social and Political Movements, ed. David A. Snow and others. (Wiley-Blackwell, Online.
Tip: Here's how to search only this title in the Wiley-Blackwell multi-title platform:
1. Click on "Search in this book."
2. Use the "Reference Works Advanced Search" and consult "tips" as needed.