Columbia subject headings:
Harvard subject headings:
Border patrols--Germany (East)--History--20th century.
Germany (East)--Boundaries--Germany (West)
Germany (East)--Politics and government.
Germany (East). Ministerium für Staatssicherheit.
Germany (West)--Boundaries--Germany (East)
Transit, International--Germany--Berlin.
Transportation--Germany--Berlin--History--20th century.
Princeton subject headings:
Border patrols--Germany (East)--History--20th century.
Germany (East)--Boundaries--Germany (West)
Germany (East)--Politics and government--20th century.
Germany (East). Ministerium für Staatssicherheit
Germany (West)--Boundaries--Germany (East)
Transit, International--Germany--Berlin.
Transportation--Germany--Berlin--History--20th century.