Z - Books and Writing 1,006
LC - Social Aspects of Education 289
E - United States History 93
PS - American Literature 69
ZA - Information Resources 66
PN - General Literature 55
PR - English Literature 49
HE - Transportation and Communications 31
C - General History 28
QE - Geology 27
D - General History 20
HQ - Family, Marriage, Women 19
HD - Industries, Land Use, Labor 17
J - General Legislature 17
DS - Asia 16
L - General Education 13
TN - Mining Engineering and Metallurgy 11
GV - Leisure and Recreation 10
F - General American History 9
GB - Physical Geography 8
HF - Commerce 7
LB - Theory and Practice of Education 7
BL - Religions, Mythology, Rationalism 6
HV - Social Pathology, Criminology 6
JZ - International Relations 6
N - Visual Arts 6
P - Philology and Linguistics 6
B - Philosophy 5
BF - Psychology 5
JK - United States 5
ND - Painting 5
BR - Christianity 4
BX - Christian Denominations 4
CT - Biography 4
G - General Geography 4
HX - Socialism, Communism, Anarchism 4
R - General Medicine 4
RC - Internal Medicine 4
AE - Encyclopedias 3
DA - Great Britain 3
DC - France, Andorra, Monaco 3
DT - Africa 3
GA - Mathematical Geography and Cartography 3
PL - Eastern Asia, Africa, Oceania 3
PQ - French, Italian, Spanish, Portuguese Literature 3
QH - Natural History and Biology 3
RA - Public Medicine 3
UB - Military Administration 3
BS - The Bible 2
CD - Diplomatics, Archives, Seals 2
DK - Russia, Soviet Union, Former Soviet Republics, Poland 2
HC - Economic History and Conditions 2
HM - Sociology 2
HN - Social History and Conditions 2
JA - Political Science 2
NK - Decorative Arts 2
PA - Latin and Greek 2
PC - Romanic Languages 2
PE - English Languages 2
PG - Slavic, Baltic, Abanian Languages 2
QK - Botany 2
QL - Zoology 2
RG - Gynecology and Obstetrics 2
TH - Building Construction 2
UA - Armies 2
VA - Navies 2
AS - Academies 1
BH - Aesthetics 1
BM - Judaism 1
BQ - Buddhism 1
CC - Archaeology 1
CR - Heraldry 1
CS - Genealogy 1
DD - Germany 1
DG - Italy, Malta 1
GN - Anthropology 1
GR - Folklore 1
HA - Statistics 1
HB - Economic Theory and Demography 1
HT - Communities, Classes, Races 1
JC - Political Theory 1
JF - Public Administration 1
JS - Local and Municipal Government 1
K - General Law 1
LA - History of Education 1
NB - Sculpture 1
NC - Drawing, Design, Illustration 1
PB - Modern and Celtic Languages 1
PM - Hyperborean, Indian, and Artificial Languages 1
Q - General Science 1
QB - Astronomy 1
QC - Physics 1
RJ - Pediatrics 1
RT - Nursing 1
S - General Agriculture 1
SB - Plant Culture 1
SF - Animal Culture 1
SK - Hunting Sports 1
T - General Technology 1
TC - Hydraulic and Ocean Engineering 1