History 279 African Americans 63 Civilization 36 Biography 34 Science 31 Experiments 30 Folklore 30 más ... Social life and customs 27 Natural history 25 Children 23 Politics and government 23 Vocational guidance 23 Women 23 Astronomy 19 Civil rights 19 Manners and customs 19 World history 19 Zoology 19 Description and travel 18 Indians of North America 17 History and criticism 16 Race relations 16 Study and teaching 16 Social conditions 15 World War, 1939-1945 15 Holocaust, Jewish (1939-1945) 14 Presidents 14 Prevention 14 Tales 14 Teenagers 14 menos ...