Classification
140 - Specific philosophical schools
1
304 - Factors affecting social behavior
333 - Economics of land & energy
1
363 - Other social problems & services
1
380 - Commerce, communications & transportation
1
551 - Geology, hydrology & meteorology
1
600 - Technology
1
620 - Engineering & allied operations
1
630 - Agriculture & related technologies
1
900 - History & geography
1