Columbia subject headings:
Astronomy--Charts, diagrams, etc.--Congresses.
Galaxies--Measurement--Congresses.
Harvard subject headings:
Astronomy
Galactic dynamics
Galaxies--Congresses
Galaxies--Formation--Congresses
Physics
Spiral galaxies--Congresses.
Princeton subject headings:
Astronomy--Charts, diagrams, etc.--Congresses.
Galaxies--Measurement--Congresses.