The following are important databases for secondary sources.
Prominent source for scholarly journal articles, book reviews, and dissertations in U.S. & Canadian history. Covers sources published from the 1960s to present.
Access scholarly journal articles, books reviews, and dissertations in modern world history (1450 to present) excluding the U.S. and Canada. Covers sources published from 1955 to present.
Official digital archive of the Library of Congress and the database of record for graduate research. Search citations to dissertations and theses from around the world from 1861 to present day, and access full text dissertations.