Número de Clasificación
T - Technology
225
H - Social Science
38
E - United States History
29
S - Agriculture
23
C - Historical Sciences
15
P - Language and Literature
15
Q - Science
5
F - General American History
4
K - Law
4
B - Philosophy, Psychology, Religion
3
D - World History
3
A - General Works
2
M - Music
2
R - Medicine
2