Classification
501 - Philosophy & theory
323
900 - History & geography
280
509 - Historical, geographic & persons treatment
275
520 - Astronomy & allied sciences
116
510 - Mathematics
112
530 - Physics
107
100 - Philosophy & psychology
82
500 - Natural sciences & mathematics
66
300 - Social sciences
56
620 - Engineering & allied operations
50
600 - Technology
49
610 - Medicine & health
49
621 - Applied physics
39
306 - Culture & institutions
37
540 - Chemistry & allied sciences
37
301 - Sociology & anthropology
32
320 - Political science
32
576 - Genetics & evolution
29
570 - Life sciences; biology
28
700 - The arts; fine & decorative arts
28
109 - Historical & collected persons treatment
25
330 - Economics
25
140 - Specific philosophical schools
24
333 - Economics of land & energy
23
120 - Epistemology, causation & humankind
22
800 - Literature & rhetoric
22
551 - Geology, hydrology & meteorology
21
200 - Religion
20
363 - Other social problems & services
20
004 - Data processing & computer science
19
612 - Human physiology
18
616 - Diseases
18
344 - Labor, social, education & cultural law
17
370 - Education
17
629 - Other branches of engineering
16
001 - Knowledge
15
304 - Factors affecting social behavior
15
150 - Psychology
13
170 - Ethics
13
190 - Modern western philosophy
13
303 - Social processes
13
338 - Production
13
507 - Education, research & related topics
13
519 - Probabilities & applied mathematics
13
809 - History, description & criticism
13
539 - Modern physics
12
940 - History of Europe
12
531 - Classical mechanics; solid mechanics
11
550 - Earth sciences
11
909 - World history
11
more ...