Classification
304 - Factors affecting social behavior
4
551 - Geology, hydrology & meteorology
4
333 - Economics of land & energy
3
341 - Law of nations
3
550 - Earth sciences
2
577 - Ecology
2
910 - Geography & travel
2
320 - Political science
1
327 - International relations
1
330 - Economics
1
363 - Other social problems & services
1