Here are three basic reference tools that every student of Classics should know about and use.
Oxford Classical Dictionary. 4th ed. New York: Oxford University Press, 2012.
Scholarly mini-encyclopedia of people, events, places in the classical world. Signed articles. Some bibliography. References to classical sources. Location: [Reference: DE5 .O9 2012] Also available Online
Paulys Real-Encyclopadie der classischen Altertumswissenschaft, neue Bearb.. 24 vols, 10 vol continuation, 15 vol supplement. Stuttgart: Metzler, 1893-1978.
The standard encyclopedia for the whole field of classical studies. Location: [Main DE 5 .P33]
See also the new edition: Der neue Pauly : Enzyklopadie der Antike. Stuttgart : J.B. Metzler, c1996- (complete in 16 vol.). Location: [Reference DE5 .P34 1996]
See also the English translation of Der neue Pauly: Brill's New Pauly : encyclopaedia of the ancient world. Hubert Cancik and Helmut Schneider, eds. Leiden ; Boston : Brill, 2002- . The English edition is divided into two print editions: Antiquity (Location: [Reference DE5 .P3413 2006] Classical Tradition (Location: [Reference DE5 .P34213]
L'Annee Philologique: bibliographie critique et analytique de l'antiquiti greco-latine. 1924- . Annual.
Major ongoing bibliography for classical studies. Covers literature, language, art, philosophy, and social political and cultural history, textual criticism, epigraphy, archeology, numismatics. Location: [Reference PA2 .A553, 1924-2000] Online version includes v.20 (1949)-present