Columbia subject headings:
Harvard subject headings:
Art, German--Germany--Cologne--Exhibitions.
Art, German--Germany--Düsseldorf--Exhibitions.
Art, Modern--20th century--Germany--Cologne--Exhibitions.
Art, Modern--20th century--Germany--Düsseldorf--Exhibitions.
Princeton subject headings:
Art, German--Exhibitions.
Art, Modern--20th century--Germany (West)--Cologne--Exhibitions.
Art, Modern--20th century--Germany (West)--Düsseldorf--Exhibitions.