Columbia subject headings:
Dependency (Psychology)--Greece--Congresses.
Dependency (Psychology)--Rome--Congresses.
Outer space--Social aspects--Greece--Congresses.
Outer space--Social aspects--Rome--Congresses.
Slavery--Greece--Congresses.
Slavery--Rome--Congresses.
Harvard subject headings:
Slavery--Greece--History--Congresses.
Slavery--Rome--History--Congresses.
Space--Social aspects--History--Congresses.
Princeton subject headings:
Slavery--Greece--History--Congresses.
Slavery--Rome--History--Congresses.
Space--Social aspects--History--Congresses.