Columbia subject headings:
Cosmology--Congresses.
Galaxies--Congresses.
Quasars--Congresses.
Harvard subject headings:
Cosmogony--Congresses.
Cosmology--Congresses.
Galaxies--Congresses
Quasars--Congresses
Princeton subject headings:
Cosmology--Congresses.
Galaxies--Congresses.
Quasars--Congresses.