Topogràfic
S - Agriculture
751
H - Social Science
531
L - Education
495
T - Technology
468
Q - Science
385
R - Medicine
244
B - Filosofia, Psicologia, Religió
201
P - Language and Literature
142
J - Political Science
102
K - Law
77
A - Treballs generalss
50
N - Fine Arts
49
G - Geography, Anthropology, Recreation
22
Z - Library Science
14
C - Historical Sciences
9
F - General American History
8
D - World History
4
E - United States History
3