Subject
Geology
5,475
Appropriations and expenditures
3,389
History
2,558
United States Foreign relations
2,536
United States Politics and government
2,363
Criticism and interpretation
2,226
Mines and mineral resources
2,202
Geology, Stratigraphic
2,161
Groundwater
1,803
Water quality
1,612
Officials and employees
1,500
Water-supply
1,430
United States History
1,421
Management
1,395
Paleontology
899
Uranium ores
898
United States Foreign economic relations
877
Indians of North America
876
Rules and practice
868
United States
848
Families
828
Frontier and pioneer life
761
African Americans
760
Selection and appointment
743
World War, 1939-1945
710
National security
703
Presidents
678
Budget
671
Land titles Registration and transfer
647
Public lands
643
National parks and reserves
616
Great Britain History
600
Forest management
590
United States Economic conditions
583
Stream measurements
582
Women
579
United States Social conditions
576
Friendship
563
English literature History and criticism
561
Hydrology
554
Hydrogeology
548
American poetry
527
Water Pollution
519
Democracy
504
American literature History and criticism
501
Water resources development
498
Bills, Legislative
494
Groundwater Pollution
489
Environmental policy
472
Drug control
460
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