Columbia subject headings:
Harvard subject headings:
Berlin (Germany)--History--1945-1990
Berlin (Germany)--History--Blockade, 1948-1949
Cold War
Internal security--Germany (East)
Princeton subject headings:
Berlin (Germany)--Politics and government--1945-1990.
Berlin Wall, Berlin, Germany, 1961-1989.
German reunification question (1949-1990)