What if a patron wants to find books on a certain subject?

Library of Congress Classification System: C-D

C-D    History, Area Studies (Lower Level)

C     Auxiliary sciences of history (General)                                                                         D     History (General)
        Europe (General)

CB: History of civilization

DA: Great Britain

CC: Archaeology

DAW: Central Europe

CD: Diplomatics, Archives, Seals

DB: Austria, Hungary, Czechoslovakia

CE: Technical chronology, Calendar

DC: France

CJ: Numismatics

DD: Germany

CN: Inscriptions, Epigraphy

DE: The Greco-Roman World

CR: Heraldry

DF: Greece

CS: Geneology

DG: Italy

CT: Biography (General)

DH: Low Countries, Benelux Countries

DJ: Netherlands (Holland)

DJK: Eastern Europe (General)

DK: Russia, Soviet Union, Former Soviet Republics, Poland

DL: Northern Europe, Scandinavia

DP: Spain, Portugal

DQ: Switzerland

DR: Balkan Peninsula, Turkey

DS: Asia

DT: Africa

DU: Oceania (South Seas)

DX: Gypsies