Columbia subject headings:
Asteroids--Congresses.
Astrometry--Congresses.
Comets--Congresses.
Interstellar matter--Congresses.
Harvard subject headings:
Asteroids--Congresses
Astrometry--Congresses
Comets--Congresses
Interstellar matter--Congresses.
Princeton subject headings:
Asteroids--Congresses.
Astrometry--Congresses.
Comets--Congresses.
Interstellar matter--Congresses.