Topogràfic
F - General American History
181
H - Social Science
137
P - Language and Literature
87
J - Political Science
67
L - Education
32
M - Music
15
B - Filosofia, Psicologia, Religió
14
K - Law
13
G - Geography, Anthropology, Recreation
10
R - Medicine
8
N - Fine Arts
7
A - Treballs generalss
6
Q - Science
5
T - Technology
4
D - World History
3
V - Naval Science
3
Z - Library Science
2
E - United States History
1
S - Agriculture
1