535 History 197 Sources 184 Government publications 169 Geology 130 Periodicals 120 History and criticism 111 Science 101 Dissertations, Academic 101 Politics and government 90 Research 89 Archives 77 Bibliography 68 Agriculture 68 Law 67 Economic conditions 60 Medicine 58 Study and teaching 55 Technology 51 Books 51 Libraries 50 Botany 49 Catalogs, Union 49 Imprints 49 Women 47 Social sciences 46 World War, 1939-1945 44 Manuscripts 42 Chemistry 42 Education 39 Russian literature