Columbia subject headings:
Harvard subject headings:
Communism--Germany--History
Socialism--Germany
Socialism--Germany--History
Working class--Germany--Political activity--History.
Working class--Political activity--Germany--History.
Working-men's clubs--Germany--History.
Princeton subject headings:
Communism--Germany--History.
Socialism--Germany--History.
Working class--Germany--Political activity--History.
Working-men's clubs--Germany--History.