Columbia subject headings:
Harvard subject headings:
Communism and Christianity--Catholic Church--History.
Communism and Christianity--Germany--History.
Labor movement--Germany--History
Labor unions--Germany--History
Socialism--Germany--History
Working class--Germany--History.
Princeton subject headings:
Communism and Christianity--Catholic Church--Germany--History.
Communism and Christianity--Germany--History.
Labor movement--Germany--History.
Labor unions--Germany--History.
Socialism--Germany--History.