Columbia subject headings:
Coal trade--Germany--Neunkirchen (Saarland)--History.
Iron industry and trade--Germany--Neunkirchen (Saarland)--History.
Steel industry and trade--Germany--Neunkirchen (Saarland)--History.
Harvard subject headings:
Coal trade--Germany--Neunkirchen (Saarland)--History.
Iron industry and trade--Germany--Neunkirchen (Saarland)--History.
Steel industry and trade--Germany--Neunkirchen (Saarland)--History.
Princeton subject headings:
Coal mines and mining--Germany (West)--Neunkirchen (Saarland).
Coke industry--Germany (West)--Neunkirchen (Saarland).
Iron industry and trade--Germany (West)--Neunkirchen (Saarland).