Columbia subject headings:
Labor movement--Germany--Rhineland--History.
Socialism--Germany--Rhineland--History.
Harvard subject headings:
Labor movement--Germany--Rhineland--History.
Socialism--Germany--Rhineland--History.
Socialism--Germany--Rhineland.
Princeton subject headings:
Labor movement--Germany (West)--Rhineland--History.
Socialism--Germany (West)--Rhineland--History.