Classification
630 - Agriculture & related technologies
3
333 - Economics of land & energy
2
000 - Computer science, information & general works
1
304 - Factors affecting social behavior
1
330 - Economics
1
363 - Other social problems & services
1
551 - Geology, hydrology & meteorology
1
581 - Specific topics in natural history
1
600 - Technology
1
620 - Engineering & allied operations
1