Columbia subject headings:
Stars--Clusters--Congresses.
Stars--Globular clusters--Congresses.
Stars--Open clusters--Congresses.
Harvard subject headings:
Physics.
Stars--Clusters--Congresses
Stars--Globular clusters--Congresses.
Stars--Open clusters--Congresses.
Princeton subject headings:
Stars--Clusters--Congresses.
Stars--Globular clusters--Congresses.
Stars--Open clusters--Congresses.