Classification
520 - Astronomy & allied sciences
707
330 - Economics
202
333 - Economics of land & energy
188
551 - Geology, hydrology & meteorology
176
523 - Specific celestial bodies & phenomena
175
500 - Natural sciences & mathematics
166
363 - Other social problems & services
151
550 - Earth sciences
110
658 - General management
108
577 - Ecology
80
910 - Geography & travel
77
338 - Production
75
530 - Physics
73
304 - Factors affecting social behavior
71
700 - The arts; fine & decorative arts
66
610 - Medicine & health
65
620 - Engineering & allied operations
63
600 - Technology
62
000 - Computer science, information & general works
55
576 - Genetics & evolution
54
300 - Social sciences
51
621 - Applied physics
51
320 - Political science
48
629 - Other branches of engineering
48
005 - Computer programming, programs & data
44
820 - English & Old English literatures
43
006 - Special computer methods
42
900 - History & geography
42
370 - Education
40
581 - Specific topics in natural history
39
004 - Data processing & computer science
35
519 - Probabilities & applied mathematics
34
630 - Agriculture & related technologies
33
331 - Labor economics
31
130 - Parapsychology & occultism
30
580 - Plants (Botany)
28
140 - Specific philosophical schools
27
570 - Life sciences; biology
27
380 - Commerce, communications & transportation
25
510 - Mathematics
23
301 - Sociology & anthropology
22
306 - Culture & institutions
19
001 - Knowledge
17
302 - Social interaction
17
332 - Financial economics
17
579 - Microorganisms, fungi & algae
17
100 - Philosophy & psychology
16
303 - Social processes
16
526 - Mathematical geography
15
540 - Chemistry & allied sciences
15
more ...