Classification
333 - Economics of land & energy
311
363 - Other social problems & services
254
330 - Economics
143
320 - Political science
61
380 - Commerce, communications & transportation
54
336 - Public finance
37
600 - Technology
23
630 - Agriculture & related technologies
15
304 - Factors affecting social behavior
10
610 - Medicine & health
10
370 - Education
6