Columbia subject headings:
Harvard subject headings:
Rome--History--Empire, 30 B.C.-284 A.D.
Rome--Politics and government--30 B.C.-284 A.D.
Rome--Politics and government--30 B.C.-284 A.D.--Congresses.
Princeton subject headings:
Opposition (Political science)--Rome--History--Empire, 30 B.C.-284 A.D.--Congresses.
Rome--History--Empire, 30 B.C.-284 A.D.--Congresses.