Reference resources are a great place to begin your research. They can help you define terms as well as to find basic information about a topic, a chronicle of its history, theories, key people and sometimes a bibliography of additional sources.
There are many different types of reference sources, which include dictionaries, encyclopedias, thesauri, bibliographies, handbooks, style manuals to name a few.
Encyclopedia of African History
The Oxford Encyclopedia of African Historiography: Methods and Sources
African Folklore: an Encyclopedia
Encyclopedia of African nations and civilizations
REF DT14 .E43 2002
Historical Dictionary of South Africa
DT766 .S23 1983
African Biographical Dictionary
DT18 .B76 1994
Bibliographies help library patrons identify books, journal articles, and other library resources on a particular subject.
Africa: a Guide to Reference Material
Stauffer REF Z3501 .M3 2007
Reference Guide to Africa: A Bibliography of Sources
Z3501 .K15 1999
African Studies Resources at the Center for Research Libraries by Center for Research Libraries
List of resources available through the Center for Research Libraries, most of which can be borrowed through Interlibrary Loans.
Bibliographies like Oxford Bibliographies offer authoritative research guides helping you to narrow the vast number of citations to the best scholarship on a given topic.
There are guides on African Studies, Atlantic History, African American Studies, and articles on e.g. Atlantic Slave Trade, Slavery in Africa to name a few.