Columbia subject headings:
Harvard subject headings:
Bergwerksgesellschaft Hibernia--History--20th century.
Cartels--Germany--Prussia--History--20th century.
Government business enterprises--Germany--Prussia--History--20th century.
Mineral industries--Germany--Ruhr (Region)--History--20th century.
Mineral industries--Government ownership--Germany--Ruhr (Region)--History--20th century.
Mining law--Germany--Prussia--History--20th century.
Prussia (Germany)--Industrial policy--History--20th century.
Princeton subject headings:
Bergwerksgesellschaft Hibernia--History--20th century.
Cartels--Germany--Prussia--History--20th century.
Government business enterprises--Germany--Prussia--History--20th century.
Mineral industries--Germany--Ruhr (Region)--History--20th century.
Mineral industries--Government ownership--Germany--Ruhr (Region)--History--20th century.
Mining law--Germany--Prussia--History--20th century..
Prussia (Germany)--Industrial policy--History--20th century.