Columbia subject headings:
Harvard subject headings:
Black market--Germany--Cologne--History--20th century--Sources.
Cologne (Germany)--Economic conditions--20th century--Sources.
Cologne (Germany)--Social conditions--20th century--Sources.
Princeton subject headings:
Black market--Germany--Cologne--History--20th century--Sources.
Cologne (Germany)--Economic conditions--20th century--Sources.
Cologne (Germany)--Social conditions--20th century--Sources.