Columbia subject headings:
Mülheim an der Ruhr (Germany). Städtisches Museum--Exhibitions.
Painting, German--20th century--Exhibitions.
Painting, German--Exhibitions.
Painting--Germany--Mülheim an der Ruhr--Exhibitions.
Ziegler, Karl--Art collections--Exhibitions.
Ziegler, Maria--Art collections--Exhibitions.
Harvard subject headings:
Art, European--Exhibitions
Art, Modern--20th century--Europe--Exhibitions.
Mülheim an der Ruhr (Germany). Städtisches Museum--Exhibitions.
Ziegler, Karl--Art collections--Exhibitions.
Ziegler, Maria--Art collections--Exhibitions.
Princeton subject headings: