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These online sources are good places to start your research.
Wikipedia is an encyclopedia written collaboratively. Though useful for basic and background information, "The upside of Wikipedia is that it is an encyclopedia that ANYONE can edit. But the downside is that it is an encyclopedia that ANYONE can edit."
Why not use Wikipedia?
If you need general information about subjects, persons, places, etc., then GVRL and Stanford Encyclopedia of Philosophy are good places to start.
Gale Virtual Reference Library (GVRL) is a collection of encyclopedias, almanacs, and specialized reference sources;these trusted, authoritative reference works are available 24/7.
Stanford Encyclopedia of Philosophy is a dynamic reference work written, refereed, and maintained by over 950 professional philosophers.