Topogràfic
F - General American History
319
H - Social Science
127
J - Political Science
64
L - Education
54
P - Language and Literature
46
K - Law
35
B - Filosofia, Psicologia, Religió
30
Q - Science
17
G - Geography, Anthropology, Recreation
14
R - Medicine
11
D - World History
10
T - Technology
10
N - Fine Arts
9
C - Historical Sciences
8
S - Agriculture
5
Z - Library Science
5
E - United States History
3
M - Music
3
A - Treballs generalss
2