Columbia subject headings:
Harvard subject headings:
Escapes--Germany (East)
Germany (East)--Emigration and immigration.
Germany (West)--Emigration and immigration
Internal security--Germany (East)
Political refugees--Germany (East)
Refugees--Germany (East)--History.
Refugees--Germany (West)--History.
Princeton subject headings:
Escapes--Germany (East).
Internal security--Germany (East)
Political refugees--Germany (East).