Columbia subject headings:
Coal mines and mining--Germany--Ruhr (Region)--Personnel management--History.
Employers' associations--Germany--Ruhr (Region)--History.
Industrial relations--Germany--Ruhr (Region)--History.
Iron industry and trade--Germany--Ruhr (Region)--Personnel management--History.
Steel industry and trade--Germany--Ruhr (Region)--Personnel management--History.
Harvard subject headings:
Coal mines and mining--Germany--Ruhr (Region)--Personnel management--History.
Employers' associations--Germany--Ruhr (Region)--History.
Industrial relations--Germany--Ruhr (Region)--History.
Iron industry and trade--Germany--Ruhr (Region)--Personnel management--History.
Steel industry and trade--Germany--Ruhr (Region)--Personnel management--History.
Princeton subject headings:
Coal mines and mining--Germany (West)--Ruhr (Region)--Personnel management--History.
Employers' associations--Germany (West)--Ruhr (Region)--History.
Industrial relations--Germany (West)--Ruhr (Region)--History.
Iron industry and trade--Germany (West)--Ruhr (Region)--Personnel management--History.
Steel industry and trade--Germany (West)--Ruhr (Region)--Personnel management--History.