Topogràfic
F - General American History
17
H - Social Science
14
L - Education
14
A - Treballs generalss
10
K - Law
6
P - Language and Literature
5
E - United States History
2
J - Political Science
2
Q - Science
2
D - World History
1
G - Geography, Anthropology, Recreation
1
T - Technology
1
Z - Library Science
1