Topogràfic
H - Social Science
93
F - General American History
48
L - Education
21
Z - Library Science
13
K - Law
8
J - Political Science
7
G - Geography, Anthropology, Recreation
6
P - Language and Literature
6
Q - Science
6
B - Filosofia, Psicologia, Religió
3
E - United States History
3
S - Agriculture
3
N - Fine Arts
2
R - Medicine
2
T - Technology
2
U - Military Science
2
A - Treballs generalss
1
M - Music
1