Politics and government -- 16 Foreign relations -- 10 History -- 7 Congresses 5 Congresses -- 5 Foreign economic relations -- 4 Economic integration 3 more ... National security -- 3 Politics and government 3 Relations -- 3 Citizenship -- 2 Commerce -- 2 Defenses 2 Defenses -- 2 Democracy -- 2 Economic conditions -- 2 Emigration and immigration -- 2 Ethnic relations 2 Ethnicity -- 2 Naturalization -- 2 Political parties -- 2 Public opinion -- 2 Social change -- 2 Aliens -- 1 Archival resources -- 1 Archives -- 1 Armed Forces -- 1 Arms control -- 1 Boundaries 1 Boundaries -- 1 less ...