Classification
330 - Economics
31
620 - Engineering & allied operations
24
616 - Diseases
18
610 - Medicine & health
17
530 - Physics
15
658 - General management
14
621 - Applied physics
13
333 - Economics of land & energy
11
006 - Special computer methods
9
541 - Physical chemistry
8
577 - Ecology
7
304 - Factors affecting social behavior
6
551 - Geology, hydrology & meteorology
6
000 - Computer science, information & general works
5
331 - Labor economics
5
580 - Plants (Botany)
5
615 - Pharmacology & therapeutics
5
140 - Specific philosophical schools
4
301 - Sociology & anthropology
4
306 - Culture & institutions
4
338 - Production
4
371 - Schools & their activities; special education
4
520 - Astronomy & allied sciences
4
571 - Physiology & related subjects
4
600 - Technology
4
700 - The arts; fine & decorative arts
4
910 - Geography & travel
4
004 - Data processing & computer science
3
300 - Social sciences
3
332 - Financial economics
3
370 - Education
3
510 - Mathematics
3
539 - Modern physics
3
570 - Life sciences; biology
3
579 - Microorganisms, fungi & algae
3
614 - Incidence & prevention of disease
3
630 - Agriculture & related technologies
3
670 - Manufacturing
3
001 - Knowledge
2
005 - Computer programming, programs & data
2
320 - Political science
2
327 - International relations
2
378 - Higher education
2
380 - Commerce, communications & transportation
2
418 - Standard usage & applied linguistics
2
518 - Numerical analysis
2
519 - Probabilities & applied mathematics
2
531 - Classical mechanics; solid mechanics
2
581 - Specific topics in natural history
2
613 - Personal health & safety
2
more ...