Columbia subject headings:
Greece--Civilization--Congresses.
Rome--Civilization--Congresses.
Slavery--History--Congresses.
Harvard subject headings:
Greece--Civilization--Congresses.
Rome--Civilization--Congresses.
Slavery--History--Congresses.
Princeton subject headings:
Greece--Civilization--Congresses.
Rome--Civilization--Congresses.
Slavery--History--Congresses.