Classification
507 - Education, research & related topics
192
370 - Education
68
500 - Natural sciences & mathematics
40
320 - Political science
20
371 - Schools & their activities; special education
19
540 - Chemistry & allied sciences
18
510 - Mathematics
17
530 - Physics
17
620 - Engineering & allied operations
14
378 - Higher education
13
330 - Economics
10
004 - Data processing & computer science
9
304 - Factors affecting social behavior
9
300 - Social sciences
7
333 - Economics of land & energy
7
006 - Special computer methods
6
303 - Social processes
6
372 - Elementary education
6
501 - Philosophy & theory
6
610 - Medicine & health
6
910 - Geography & travel
6
306 - Culture & institutions
5
331 - Labor economics
5
570 - Life sciences; biology
5
621 - Applied physics
5
650 - Management & auxiliary services
5
001 - Knowledge
4
003 - Systems
4
338 - Production
4
340 - Law
4
660 - Chemical engineering
4
301 - Sociology & anthropology
3
363 - Other social problems & services
3
509 - Historical, geographic & persons treatment
3
520 - Astronomy & allied sciences
3
547 - Organic chemistry
3
551 - Geology, hydrology & meteorology
3
607 - Education, research & related topics
3
302 - Social interaction
2
327 - International relations
2
541 - Physical chemistry
2
550 - Earth sciences
2
571 - Physiology & related subjects
2
576 - Genetics & evolution
2
577 - Ecology
2
580 - Plants (Botany)
2
612 - Human physiology
2
614 - Incidence & prevention of disease
2
617 - Surgery & related medical specialties
2
624 - Civil engineering
2
more ...