Encyclopedias are great for:
Specialized Scholarly Subject Encyclopedias: Middle Ages & Renaissance
Dictionary of the Middle Ages. 12 vols. 1982-1988. (Olin Reference D 114 D55+)
Articles cover roughly the years 500-1500 A.D. in the lands of the Latin West, the Slavic world, Asia Minor, the lands of the Caliphate in the East, and the Muslim-Christian areas of North Africa. Some entries are only of definition length (e.g. Avignon), but others are more historical and lengthy (e.g. Byzantine Empire, Constantine I, Arms and Armor). Bibliographies are mostly in English.
Encyclopedia of traditional epics (Olin Library Reference Oversize PN56.E65 E64x 1994 +)
The Catholic encyclopedia (Olin Library Oversize BX841 .C36 +) and The New Catholic Encyclopedia
Goes beyond the subject of Catholicism to include science, literature, art and civilization. Articles sometimes include bibliography of primary and secondary sources.
The Wiley Blackwell Encyclopedia of Anglo-Saxon England. 2nd ed.
People, places, social groups. Most articles contain concise bibliographies.
Medieval Italy: an encyclopedia (Olin Library Reference DG443 .M43x 2004 +)
Medieval England: An Encyclopedia. 1998.(Olin Reference DA 129 .M43x 1998)
Articles vary in length but all are accompanied by bibliographies.