Columbia subject headings:
Harvard subject headings:
Germany--Economic conditions--19th century--Congresses.
Germany--Economic conditions--20th century--Congresses.
Germany--Social life and customs--19th century--Congresses.
Germany--Social life and customs--20th century--Congresses.
Middle class--Germany--History--19th century--Congresses.
Middle class--Germany--History--20th century--Congresses.
Princeton subject headings:
Germany--Social life and customs--19th century--Congresses.
Germany--Social life and customs--20th century--Congresses.
Middle class--Germany--History--19th century--Congresses.
Middle class--Germany--History--20th century--Congresses.