Columbia subject headings:
Harvard subject headings:
Halstenberg, Friedrich.
North Rhine-Westphalia (Germany)--Economic conditions.
North Rhine-Westphalia (Germany)--Politics and government.
Political planning--Germany--North Rhine-Westphalia.
Regional planning--Germany--North Rhine-Westphalia.
Princeton subject headings:
Halstenberg, Friedrich.
North Rhine-Westphalia (Germany)--Economic conditions.
Regional planning--Germany--North Rhine-Westphalia.