Classification
551 - Geology, hydrology & meteorology
26
577 - Ecology
14
550 - Earth sciences
6
910 - Geography & travel
5
363 - Other social problems & services
4
620 - Engineering & allied operations
3
820 - English & Old English literatures
3
900 - History & geography
3
000 - Computer science, information & general works
2
320 - Political science
2
333 - Economics of land & energy
2
341 - Law of nations
2
500 - Natural sciences & mathematics
2
570 - Life sciences; biology
2
580 - Plants (Botany)
2
590 - Animals (Zoology)
2
621 - Applied physics
2
327 - International relations
1
330 - Economics
1
344 - Labor, social, education & cultural law
1
355 - Military science
1
380 - Commerce, communications & transportation
1
520 - Astronomy & allied sciences
1
530 - Physics
1
540 - Chemistry & allied sciences
1
560 - Paleontology; paleozoology
1
571 - Physiology & related subjects
1
578 - Natural history of organisms
1
581 - Specific topics in natural history
1
591 - Specific topics in natural history
1
629 - Other branches of engineering
1
700 - The arts; fine & decorative arts
1
800 - Literature & rhetoric
1