Columbia subject headings:
Europe--Foreign relations--Germany (West)
Germany (West)--Foreign relations--Europe.
North Rhine-Westphalia (Germany)--Politics and government.
Ruhr (Germany : Region)
Harvard subject headings:
Europe--Foreign relations--Germany (West)
Germany (West)--Foreign relations--Europe.
North Rhine-Westphalia (Germany)--Politics and government.
Ruhr (Germany : Region)
Princeton subject headings:
North Rhine-Westphalia (Germany)--Politics and government.
Ruhr (Germany : Region)--Politics and government.