Columbia subject headings:
Harvard subject headings:
Multilingualism--Germany--Ruhr (Region)
Public spaces--Germany--Ruhr (Region)
Signs and signboards--Germany--Ruhr (Region)
Princeton subject headings:
Multilingualism--Germany--Ruhr (Region)--Pictorial works.
Multilingualism--Germany--Ruhr (Region).
Ruhr (Germany : Region)--Social life and customs--21st century--Pictorial works.
Ruhr (Germany : Region)--Social life and customs--21st century.
Signs and symbols--Social aspects--Germany--Ruhr (Region)--Pictorial works.
Signs and symbols--Social aspects--Germany--Ruhr (Region).