Columbia subject headings:
Harvard subject headings:
Germany (West)--Politics and government.
Political activists--Germany--Ruhr (Region)
Radicalism--Germany--Ruhr (Region)--History--20th century.
Ruhr (Germany : Region)--Social conditions
Social movements--Germany--Ruhr (Region)--History--20th century.
Princeton subject headings:
Germany (West)--Politics and government.
Political activists--Germany--Ruhr (Region).
Radicalism--Germany--Ruhr (Region)--History--20th century.
Ruhr (Germany : Region)--Social conditions.
Social movements--Germany--Ruhr (Region)--History--20th century.