Columbia subject headings:
Harvard subject headings:
Coal mines and mining--Germany--Bottrop--History.
Coal trade--Germany--Bottrop--History.
Verbundbergwerk Prosper-Haniel--History.
Princeton subject headings:
Bottrop (Germany)--History.
Mineral industries--Germany--Bottrop--History.
Mines and mineral resources--Germany--Bottrop--History.
Verbundbergwerk Prosper-Haniel.