Columbia subject headings:
Mine subsidences--Germany--Ruhr (Region)
Subsidences (Earth movements)--Germany--Ruhr (Region)
Harvard subject headings:
Geomorphology--Germany--Ruhr (Region)
Groundwater--Environmental aspects--Germany--Ruhr (Region)
Mine subsidences--Germany--Ruhr (Region)
Subsidences (Earth movements)--Germany--Ruhr (Region)
Princeton subject headings:
Geomorphology--Germany--Ruhr (Region).
Groundwater--Environmental aspects--Germany--Ruhr (Region).
Mine subsidences--Germany--Ruhr (Region).
Subsidences (Earth movements)--Germany--Ruhr (Region).