Columbia subject headings:
Absorption spectra--Congresses.
Galaxies--Congresses.
Quasars--Spectra--Congresses.
Harvard subject headings:
Absorption spectra--Congresses.
Galaxies--Congresses
Quasars--Spectra--Congresses.
Princeton subject headings:
Absorption spectra--Congresses.
Galaxies--Congresses.
Quasars--Spectra--Congresses.