Below are links to reference sources and collections that are most useful for this subject:
These databases search the indexes and tables of contents of multiple reference books at once.
These are key reference works in European History.
Reference sources can include encyclopedias, bibliographies, dictionaries, handbooks, and atlases.
You can find the Library's collection of reference books on Floor 1 of Frost. We also have many online databases that include collections of edited scholarly encyclopedias, dictionaries, and other reference sources.