Subject
Geology
27
Law
19
Mines and mineral resources
16
Government publications
14
Paleontology
11
History
8
United States History
6
Uranium ores
6
Coal
5
Debates and debating
5
English literature
5
Hydrology
5
Reference books
5
American literature
4
Authors, American
4
Children's literature, American
4
Climatic changes
4
Coal mines and mining
4
Geology, Stratigraphic
4
Groundwater
4
Materials Fatigue
4
Music History and criticism
4
Officials and employees
4
Paleobotany
4
Working class
4
Automation
3
Chemistry, Organic
3
Clay
3
English-speaking countries In literature
3
English-speaking countries Intellectual life
3
Environmental policy
3
Geochemistry
3
Humanities
3
Humanities Reference books
3
Leadership
3
Legal research
3
Maps
3
Mathematics
3
Medicine
3
Mollusks, Fossil
3
Nuclear explosions
3
Occupations
3
Paleobotany Nomenclature
3
Plant ecology
3
Power resources
3
Printing History
3
Sources
3
Thorium
3
Vegetation management
3
Vocational guidance
3
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