Columbia subject headings:
Art and science--Congresses.
Escher, M. C. (Maurits Cornelis), 1898-1972--Criticism and interpretation--Congresses.
Harvard subject headings:
Art and science--Congresses
Escher, M. C. (Maurits Cornelis), 1898-1972--Criticism and interpretation--Congresses.
Princeton subject headings:
Art and science--Congresses.
Escher, M. C. (Maurits Cornelis), 1898-1972--Criticism and interpretation--Congresses.