Columbia subject headings:
Industries--Germany--Bergisches Land--History.
Labor unions--Germany--Bergisches Land--History.
Labor--Germany--Bergisches Land--History.
Harvard subject headings:
Industries--Germany--Bergisches Land--History.
Labor unions--Germany--Bergisches Land--History.
Working class--Germany--Bergisches Land--History.
Princeton subject headings:
Industries--Germany--Bergisches Land--History.
Labor unions--Germany--Bergisches Land--History.
Working class--Germany--Bergisches Land--History.