Subject
United States History
66
United States Politics and government
28
United States Economic conditions
20
Depressions
19
Physical geography
17
Indians of North America History
15
Leadership
14
Management
14
African Americans History
12
Immigrants
12
Civilization, Ancient
11
Labor History
11
African Americans Social life and customs
10
Industries History
10
Music History and criticism
10
Musical form
10
Social structure
10
Sports
10
Style, Musical
10
United States Territorial expansion
10
Antiquities
9
Civil rights movements History
9
Culture
9
Natural resources
9
Imperialism History
8
India
8
Political planning
8
Power (Social sciences)
8
World War, 1939-1945
8
Constitutional history
7
Energy consumption
7
Energy development
7
Ethnicity
7
History, Modern
7
Learning, Psychology of
7
Natural resources Management
7
Political participation
7
Power resources Environmental aspects
7
Social policy
7
Technology Industrial applications
7
Adolescent psychopathology
6
Astronomy
6
Child development
6
Children with disabilities Education
6
Children with social disabilities Education
6
Christianity
6
Conservation of natural resources
6
Conservation of natural resources Government policy
6
Educational psychology
6
Environmental policy
6
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