Reference books are usually encyclopedias, dictionaries, handbooks, atlases, etc. They are intended to provide quick, reliable information, summaries of complex matters, and, very importantly, bibliographies--suggestions for further reading.
Historical sources:
Medieval Italy: An Encyclopedia DG443 .M43 2004
A Concise encyclopaedia of the Italian Renaissance DG445 .C66 1981
Italy:a reference guide from the Renaissance to the present DG461 .S27 2004
The New Century Italian Renaissance encyclopedia DG537.8.A1 N48
Dictionary of the Middle Ages D114 .D5 1982 +
Europe 1450 to 1789 : encyclopedia of the early modern world D209 .E97 2004 +
The Oxford dictionary of the Renaissance CB361 .C27 2003
Encyclopedia of the Renaissance and the Reformation CB359 .B47 2004
The late medieval age of crisis and renewal, 1300-1500 : a biographical dictionary CB353 .L38 2001
Dictionary of medieval civilization CB351 .D24 1984
Literary sources:
Dictionary of Italian literature PQ4006 .D45
Dizionario enciclopedico della letteratura italiana PQ4006 .D5
The Oxford companion to Italian literature PQ4006 .O84 2002
The Cambridge history of Italian literature PQ4038 .C36 1999
Dizionario critico della letteratura italiana PQ4057 .D59 1986
The Dante Encyclopedia PQ4333 .D36 2000
Ecclesiastical sources:
New Catholic encyclopedia BX841 .N44 2003 +
The papacy : an encyclopedia BX955.3 .D5313 2002 +
The Oxford dictionary of saints BR1710 .F34 1987
The encyclopedia of Christianity BR95 .E8913 1999
The Oxford dictionary of the Christian Church BR95 .O8 1997
Classical sources:
Brill's New Pauly : encyclopaedia of the ancient world DE5 .N4813 2002
The Oxford companion to classical civilization DE5 .O92 1998
Dictionary of Greek and Roman biography and mythology DE5 .S7 1867
