Columbia subject headings:
Galaxies--Congresses.
Nuclear astrophysics--Congresses.
Quasars--Congresses.
Harvard subject headings:
Galactic nuclei--Congresses.
Nuclear astrophysics--Congresses.
Quasars--Congresses
Princeton subject headings:
Galaxies--Congresses.
Nuclear astrophysics--Congresses.
Quasars--Congresses.