Columbia subject headings:
Harvard subject headings:
Active galactic nuclei--Congresses.
Galactic nuclei--Congresses.
Seyfert galaxies--Congresses.
Princeton subject headings:
Active galaxies--Congresses.
Galactic nuclei--Congresses.
Radio astronomy--Congresses.
Seyfert galaxies--Congresses.
X-ray astronomy--Congresses.