A --General Works

M --Music

B --Philosophy, Psychology, Religion

N --Fine Arts

C --Civilization, Archaeology

P --Language and Literature

D --World History

Q --Science

E --History of the Americas

R --Medicine

F --History of the Americas

S --Agriculture

G --Geography, Anthropology

T --Technology

H --Social Sciences

U --Military Science

J --Political Science

V --Naval Science

K --Law

Z --Library Science, Bibliography

L --Education