Classification
577 - Ecology
215
333 - Economics of land & energy
109
580 - Plants (Botany)
48
630 - Agriculture & related technologies
44
551 - Geology, hydrology & meteorology
36
581 - Specific topics in natural history
36
363 - Other social problems & services
29
910 - Geography & travel
27
304 - Factors affecting social behavior
23
610 - Medicine & health
23
000 - Computer science, information & general works
22
570 - Life sciences; biology
19
634 - Orchards, fruits & forestry
19
550 - Earth sciences
17
576 - Genetics & evolution
17
003 - Systems
15
591 - Specific topics in natural history
15
380 - Commerce, communications & transportation
13
578 - Natural history of organisms
11
620 - Engineering & allied operations
11
700 - The arts; fine & decorative arts
11
500 - Natural sciences & mathematics
10
330 - Economics
9
579 - Microorganisms, fungi & algae
9
140 - Specific philosophical schools
8
600 - Technology
8
301 - Sociology & anthropology
7
612 - Human physiology
6
631 - Techniques, equipment & materials
6
800 - Literature & rhetoric
6
305 - Social groups
5
540 - Chemistry & allied sciences
5
592 - Invertebrates
5
006 - Special computer methods
4
414 - Phonology & phonetics
4
571 - Physiology & related subjects
4
100 - Philosophy & psychology
3
300 - Social sciences
3
519 - Probabilities & applied mathematics
3
628 - Sanitary & municipal engineering
3
900 - History & geography
3
306 - Culture & institutions
2
510 - Mathematics
2
515 - Analysis
2
530 - Physics
2
560 - Paleontology; paleozoology
2
572 - Biochemistry
2
590 - Animals (Zoology)
2
621 - Applied physics
2
636 - Animal husbandry
2
more ...