Classification
330 - Economics
101
500 - Natural sciences & mathematics
68
300 - Social sciences
62
004 - Data processing & computer science
61
620 - Engineering & allied operations
61
621 - Applied physics
58
577 - Ecology
56
616 - Diseases
56
005 - Computer programming, programs & data
52
320 - Political science
52
006 - Special computer methods
45
551 - Geology, hydrology & meteorology
43
510 - Mathematics
42
333 - Economics of land & energy
41
501 - Philosophy & theory
36
900 - History & geography
36
617 - Surgery & related medical specialties
32
001 - Knowledge
31
520 - Astronomy & allied sciences
30
580 - Plants (Botany)
30
610 - Medicine & health
29
530 - Physics
28
658 - General management
28
550 - Earth sciences
27
664 - Food technology
27
519 - Probabilities & applied mathematics
25
340 - Law
24
641 - Food & drink
24
910 - Geography & travel
24
363 - Other social problems & services
23
301 - Sociology & anthropology
22
304 - Factors affecting social behavior
22
306 - Culture & institutions
21
338 - Production
20
570 - Life sciences; biology
18
331 - Labor economics
17
509 - Historical, geographic & persons treatment
17
576 - Genetics & evolution
17
302 - Social interaction
15
612 - Human physiology
15
624 - Civil engineering
15
571 - Physiology & related subjects
14
650 - Management & auxiliary services
14
327 - International relations
13
600 - Technology
13
511 - General principles of mathematics
12
572 - Biochemistry
12
515 - Analysis
11
670 - Manufacturing
11
523 - Specific celestial bodies & phenomena
10
more ...