Topogràfic
Q - Science
983
S - Agriculture
130
R - Medicine
90
T - Technology
38
G - Geography, Anthropology, Recreation
19
H - Social Science
16
B - Filosofia, Psicologia, Religió
14
L - Education
6
U - Military Science
3
Z - Library Science
3
N - Fine Arts
2
P - Language and Literature
2
J - Political Science
1
K - Law
1