Columbia subject headings:
Chemical industry--Germany--Oberhausen (Düsseldorf)--Exhibitions.
Photography, Industrial--Germany--Oberhausen (Düsseldorf)--Exhibitions.
Ruhrchemie Aktiengesellschaft--Exhibitions.
Harvard subject headings:
Princeton subject headings:
Chemical industry--Germany--Oberhausen (Düsseldorf)--History--Pictorial works--Exhibitions.
Photography, Artistic.
Ruhrchemie Aktiengesellschaft--Pictorial works--Exhibitions.