Columbia subject headings:
Communism--History.
Socialism--Germany--History.
Working class--Germany--History.
Harvard subject headings:
Communism--History
Labor and laboring classes--Germany--History.
Labor--Germany--History.
Socialism--Germany
Socialism--Germany--History
Working class--Germany--History.
Princeton subject headings:
Communism--History.
Socialism--Germany--History.
Working class--Germany--History.