Topogràfic
Q - Science
40
H - Social Science
33
P - Language and Literature
29
B - Filosofia, Psicologia, Religió
24
R - Medicine
24
D - World History
20
T - Technology
13
G - Geography, Anthropology, Recreation
8
J - Political Science
8
L - Education
6
S - Agriculture
6
K - Law
5
M - Music
5
N - Fine Arts
5
A - Treballs generalss
2
E - United States History
1
Z - Library Science
1