Columbia subject headings:
Harvard subject headings:
Germany--History.
Germany--Social conditions.
Middle class--Europe--History.
Middle class--Germany--History
Middle class--Political activity--Europe--History.
Middle class--Political activity--Germany--History.
Princeton subject headings:
Germany--Social conditions.
Middle class--Europe--History.
Middle class--Germany--History.
Middle class--Political activity--Europe--History.
Middle class--Political activity--Germany--History.