Columbia subject headings:
Harvard subject headings:
Andromeda Galaxy--Congresses.
Interstellar matter--Congresses.
Local Group (Astronomy)--Congresses.
Triangulum Galaxy--Congresses.
Princeton subject headings:
Andromeda Galaxy--Congresses.
Interstellar matter--Congresses.
Local Group (Astronomy)--Congresses.
Triangulum Galaxy--Congresses.