Columbia subject headings:
Socialism--Germany--History--Sources.
Socialism--Germany--History.
Working class--Political activity--Germany--History--Sources.
Working class--Political activity--Germany--History.
Harvard subject headings:
Labor movement--Germany--History
Labor movement--Germany--History--Sources.
Socialism--Germany
Socialism--Germany--History
Socialism--Germany--History--Sources.
Socialism--Germany--Sources.
Princeton subject headings: