Topogràfic
L - Education
649
H - Social Science
340
Q - Science
338
R - Medicine
179
B - Filosofia, Psicologia, Religió
151
T - Technology
121
S - Agriculture
108
P - Language and Literature
56
J - Political Science
40
G - Geography, Anthropology, Recreation
35
K - Law
29
A - Treballs generalss
22
Z - Library Science
17
N - Fine Arts
15
D - World History
10
C - Historical Sciences
8
F - General American History
2