Topogràfic
L - Education
429
H - Social Science
36
K - Law
27
G - Geography, Anthropology, Recreation
16
Q - Science
15
T - Technology
10
B - Filosofia, Psicologia, Religió
6
S - Agriculture
4
F - General American History
3
P - Language and Literature
3
M - Music
2
N - Fine Arts
2
R - Medicine
1
Z - Library Science
1