History 16 Description and travel 5 Continental drift 3 Documentary television programs 3 Films for the hearing impaired 3 Historical geology 3 Inventions 3 Plate tectonics 3 Study and teaching (Elementary) 3 Technology 3 Anthropology 2 Children's literature 2 Evaluation 2 Fairy tales 2 Families 2 Feature films 2 Friendship 2 Genocide 2 History and criticism 2 Human ecology 2 Law and legislation 2 Nonfiction films 2 Origin 2 Politics and government 2 Psychological aspects 2 Rock musicians 2 Teacher-student relationships 2 Technology and civilization 2 Travel 2 Volcanoes 2