History 510 Politics and government 342 Periodicals 262 Economic conditions 208 Foreign relations 121 Biography 119 Social conditions 102 Congresses 90 Communism 77 Description and travel 70 Social life and customs 69 Economic policy 68 History and criticism 66 Agriculture 62 Education 57 Bibliography 50 Geology 46 Research 45 World War, 1939-1945 45 Fiction 44 Civilization 43 Philosophy 39 Science 38 Statistics 35 Criticism and interpretation 34 Economic aspects 33 Forests and forestry 33 Mathematics 33 Economics 32 Sources 32