Columbia subject headings:
Harvard subject headings:
Coal mines and mining--Germany (East)--History.
Coal trade--Germany (East)--History.
Energy industries--Germany (East)--History.
Power resources--Germany (East)--History.
Princeton subject headings:
Coal mines and mining--Germany (East)--History.
Coal trade--Germany (East)--History.
Energy industries--Germany (East)--History.
Power resources--Germany (East)--History.