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.
Oxford Reference Online - History
♦ Oxford Dictionary of Byzantium
♦ Dictionary of British History
♦ Oxford Dictionary of Islam
♦ Oxford Dictonary of the Renaissance
♦ Encyclopedia of the Middle Ages.
Atlas of the Crusades
G1034 .R5 1991 (Maps & Air Photos)
Dictionary of the Middle Ages
REF D114 .D5 1982 plus supplement
Encyclopaedia Islamica
In progress. Expected completion in 2028.
Encyclopedia of Islam
Aims to be a comprehensive reference work in English on all aspects of Islam written by leading scholars.
New Catholic Encyclopedia
REF BX841 .N44 2003
The older edition (1907-1912) can be found online.
The Routledge Encyclopedias of the Middle Ages (series)
Key Figures in Medieval Europe: an Encyclopedia
REF D115 .E56 2006
The titles in Cambridge Histories Online will give you scholarly overviews and enhance any aspect of historical research. Includes the following titles:
The New Cambridge Medieval History
Cambridge History of the Byzantine Empire, ca. 500-1492
Cambridge History of Christianity
The New Cambridge History of Islam
Bibliography of English Translations from Medieval Sources, by Clarissa P. Farrar and Austin P. Evans. New York, Columbia University Press, 1946.
REF PN665.2 F2
Bibliography of English Translations from Medieval Sources, 1943-1967, by Mary Anne Heyward Ferguson. New York, Columbia University Press, 1974.
REF Z6517 .F47
Oxford Bibliographies offers peer reviewed annotated bibliographies which will help you to narrow the vast number of citations to the best scholarship on a given topic.
Bibliographies are browsable by subject area and keyword searchable.
For example, there is a research guide on Medieval Studies as well as an essay on The Crusades and the Ayyubids.
Within The Crusades essay, there is a section on major Primary Source Collections and Primary Source Collections in Translation.