Classification
330 - Economics
149
900 - History & geography
42
320 - Political science
38
551 - Geology, hydrology & meteorology
22
333 - Economics of land & energy
20
577 - Ecology
16
700 - The arts; fine & decorative arts
16
363 - Other social problems & services
15
820 - English & Old English literatures
11
972 - Middle America; Mexico
11
327 - International relations
10
338 - Production
10
600 - Technology
10
930 - History of ancient world to ca. 499
10
300 - Social sciences
9
301 - Sociology & anthropology
9
304 - Factors affecting social behavior
9
000 - Computer science, information & general works
8
370 - Education
8
581 - Specific topics in natural history
8
800 - Literature & rhetoric
8
400 - Language
7
306 - Culture & institutions
6
140 - Specific philosophical schools
5
305 - Social groups
5
380 - Commerce, communications & transportation
5
580 - Plants (Botany)
5
610 - Medicine & health
5
630 - Agriculture & related technologies
5
658 - General management
5
910 - Geography & travel
5
200 - Religion
4
303 - Social processes
4
414 - Phonology & phonetics
4
570 - Life sciences; biology
4
576 - Genetics & evolution
4
634 - Orchards, fruits & forestry
4
970 - History of North America
4
340 - Law
3
362 - Social welfare problems & services
3
616 - Diseases
3
770 - Photography, photographs & computer art
3
004 - Data processing & computer science
2
100 - Philosophy & psychology
2
331 - Labor economics
2
336 - Public finance
2
410 - Linguistics
2
550 - Earth sciences
2
613 - Personal health & safety
2
617 - Surgery & related medical specialties
2
more ...