Columbia subject headings:
Labor unions--Germany--Ruhr (Region)--History.
Ruhr (Germany : Region)--History--French occupation, 1923-1925.
Harvard subject headings:
Germany--History--Allied occupation, 1918-1930.
Labor unions--Germany--History
Princeton subject headings:
Labor unions--Germany (West)--Ruhr (Region)--History.
Ruhr (Germany : Region)--History--French occupation, 1923-1925.