Columbia subject headings:
Astronomy--Philosophy--Congresses.
Cosmology--Congresses.
Zwicky, F. (Fritz), 1898-1974.
Harvard subject headings:
Astronomy
Astronomy--Philosophy--Congresses.
Astrophysics
Cosmology--Congresses.
Physical geography.
Physics.
Zwicky, F. (Fritz), 1898-
Zwicky, F. (Fritz), 1898-1974.
Princeton subject headings:
Astronomy--Philosophy--Congresses.
Cosmology--Congresses.
Zwicky, F. (Fritz), 1898-1974.