Columbia subject headings:
Coal mines and mining--France--Nord-Pas-de-Calais--Pictorial works.
Coal trade--France--Nord-Pas-de-Calais--Pictorial works.
Harvard subject headings:
Coal mines and mining--France--Nord-Pas-de-Calais--Pictorial works.
Coal trade--France--Nord-Pas-de-Calais--Pictorial works.
Princeton subject headings: