Columbia subject headings:
Harvard subject headings:
Cologne (Germany)--Social conditions--19th century.
Cologne (Germany)--Social conditions--20th century.
Cologne (Germany)--Social life and customs--19th century.
Cologne (Germany)--Social life and customs--20th century.
Working class--Germany--Cologne--Social conditions--19th century.
Working class--Germany--Cologne--Social conditions--20th century.
Princeton subject headings:
Cologne (Germany)--Social conditions--19th century.
Cologne (Germany)--Social conditions--20th century.
Cologne (Germany)--Social life and customs--19th century.
Cologne (Germany)--Social life and customs--20th century.
Working class--Germany--Cologne--Social conditions--19th century.
Working class--Germany--Cologne--Social conditions--20th century.