History 845 Politics and government 223 Revolutions 88 Economic conditions 78 Communism 73 Social conditions 73 Foreign relations 60 Socialism 57 Causes 42 History and criticism 39 Sources 39 Biography 36 Agriculture 31 Economic aspects 28 Industries 26 Economic policy 25 Science 22 Personal narratives 18 Working class 18 Commerce 17 Congresses 17 United States 17 Philosophy 16 Social life and customs 16 Church history 15 Economics 14 Education 14 Foreign public opinion 14 Political activity 14 Political science 14