Finding Secondary Sources
Historical Abstracts (1954- ) includes books, book chapters, and journal articles (no book reviews) on world history excluding North America.
America: History and Life (1964- ) includes books, book chapters, journal articles, and book reviews on North American history.
Bibliography of British and Irish History (BBIH) is a comprehensive bibliography of books and periodical articles on British history.
History of Science, Technology and Medicine For a search guide and other history of science indexes.
Web of Science Citation Indexes allow citation searching, that is, starting with an article of interest and finding more recent articles that have cited it. More information.
JSTOR offers full-text of complete runs (up to about 5 years ago) of over 400 journals. Allows simultaneous or individual searching, full-text searching optional, of many historical journals.