Classification
333 - Economics of land & energy
225
500 - Natural sciences & mathematics
48
551 - Geology, hydrology & meteorology
41
577 - Ecology
38
621 - Applied physics
28
363 - Other social problems & services
24
550 - Earth sciences
20
910 - Geography & travel
17
570 - Life sciences; biology
16
572 - Biochemistry
14
620 - Engineering & allied operations
14
320 - Political science
13
624 - Civil engineering
10
628 - Sanitary & municipal engineering
10
634 - Orchards, fruits & forestry
8
304 - Factors affecting social behavior
6
571 - Physiology & related subjects
6
630 - Agriculture & related technologies
6
300 - Social sciences
3
581 - Specific topics in natural history
3
610 - Medicine & health
3
613 - Personal health & safety
3
614 - Incidence & prevention of disease
3
631 - Techniques, equipment & materials
3
660 - Chemical engineering
3
003 - Systems
2
301 - Sociology & anthropology
2
541 - Physical chemistry
2
549 - Mineralogy
2
560 - Paleontology; paleozoology
2
580 - Plants (Botany)
2
809 - History, description & criticism
2
900 - History & geography
2
004 - Data processing & computer science
1
005 - Computer programming, programs & data
1
006 - Special computer methods
1
142 - Critical philosophy
1
303 - Social processes
1
327 - International relations
1
330 - Economics
1
338 - Production
1
344 - Labor, social, education & cultural law
1
515 - Analysis
1
518 - Numerical analysis
1
519 - Probabilities & applied mathematics
1
520 - Astronomy & allied sciences
1
523 - Specific celestial bodies & phenomena
1
530 - Physics
1
540 - Chemistry & allied sciences
1
546 - Inorganic chemistry
1
more ...