Topogràfic
H - Social Science
18
R - Medicine
15
P - Language and Literature
13
D - World History
11
Q - Science
10
T - Technology
8
B - Filosofia, Psicologia, Religió
7
G - Geography, Anthropology, Recreation
6
J - Political Science
5
C - Historical Sciences
4
K - Law
3
S - Agriculture
3
A - Treballs generalss
2
Z - Library Science
2
N - Fine Arts
1