Classification
500 - Natural sciences & mathematics
20
510 - Mathematics
13
629 - Other branches of engineering
9
306 - Culture & institutions
7
509 - Historical, geographic & persons treatment
7
519 - Probabilities & applied mathematics
7
520 - Astronomy & allied sciences
7
530 - Physics
6
621 - Applied physics
5
320 - Political science
4
516 - Geometry
4
616 - Diseases
4
004 - Data processing & computer science
3
150 - Psychology
3
302 - Social interaction
3
330 - Economics
3
333 - Economics of land & energy
3
501 - Philosophy & theory
3
539 - Modern physics
3
641 - Food & drink
3
658 - General management
3
664 - Food technology
3
006 - Special computer methods
2
155 - Differential & developmental psychology
2
361 - Social problems & social welfare in general
2
370 - Education
2
523 - Specific celestial bodies & phenomena
2
551 - Geology, hydrology & meteorology
2
570 - Life sciences; biology
2
610 - Medicine & health
2
100 - Philosophy & psychology
1
120 - Epistemology, causation & humankind
1
128 - Humankind
1
301 - Sociology & anthropology
1
305 - Social groups
1
327 - International relations
1
332 - Financial economics
1
345 - Criminal law
1
364 - Criminology
1
378 - Higher education
1
507 - Education, research & related topics
1
512 - Algebra
1
515 - Analysis
1
535 - Light & infrared & ultraviolet phenomena
1
537 - Electricity & electronics
1
540 - Chemistry & allied sciences
1
576 - Genetics & evolution
1
579 - Microorganisms, fungi & algae
1
580 - Plants (Botany)
1
591 - Specific topics in natural history
1
more ...