Classification
500 - Natural sciences & mathematics
551 - Geology, hydrology & meteorology
3
600 - Technology
3
620 - Engineering & allied operations
3
900 - History & geography
333 - Economics of land & energy
2
363 - Other social problems & services
2
610 - Medicine & health
2
700 - The arts; fine & decorative arts
2
330 - Economics
1
581 - Specific topics in natural history
1
630 - Agriculture & related technologies
1