Columbia subject headings:
Harvard subject headings:
Coal miners--Germany--Ruhr (Region)--History.
Coal mines and mining--Germany--Ruhr (Region)--History.
Collective memory--Germany--Ruhr (Region)
Labor--Germany--Ruhr (Region)--History.
Ruhr (Germany : Region)--Social conditions
Princeton subject headings:
Coal miners--Germany--Ruhr (Region)--History.
Coal mines and mining--Germany--Ruhr (Region)--History.
Collective memory--Germany--Ruhr (Region).
Labor--Germany--Ruhr (Region)--History.
Ruhr (Germany : Region)--Social conditions.