Find these searching NUcat for your search term plus words like encyclopedias, handbooks, dictionaries, bibliographies, guides, or companions.
Available online unless otherwise noted.
Think of a reference resource as a bird's-eye overview of your topic. A reference (or tertiary) resource compiles, analyzes, digests, and categorizes secondary and primary sources. This chart from the University of North Carolina has excellent examples of primary, secondary, and tertiary sources. Remember to properly cite your sources to avoid plagiarism.
Remember, reference sources will frequently be classified as encyclopedias, handbooks, dictionaries, bibliographies, guides, or companions.
While not always a traditional reference source, books classified as "histories" often give a good broad overview of a topic. In library catalogs, the key subject term to add to your search is "history"; you'll find not only specific books but well-known series like the Cambridge Histories.