Columbia subject headings:
Canals--Germany (West)
North Rhine-Westphalia (Germany)--History.
Ruhr (Germany : Region)--History.
World War, 1939-1945--Territorial questions--Germany.
Harvard subject headings:
Canals--Germany
North Rhine-Westphalia (Germany)--History.
Ruhr (Germany : Region)--History
World War, 1939-1945--Territorial questions--Germany.
Princeton subject headings:
Canals--Germany.
North Rhine-Westphalia (Germany)--History.
Ruhr (Germany : Region)--History.
World War, 1939-1945--Territorial questions--Germany.