Topogràfic
Z - Library Science
51
B - Filosofia, Psicologia, Religió
25
H - Social Science
22
Q - Science
21
S - Agriculture
18
R - Medicine
17
F - General American History
13
J - Political Science
13
D - World History
8
L - Education
8
T - Technology
6
G - Geography, Anthropology, Recreation
4
K - Law
2
M - Music
1
P - Language and Literature
1