Columbia subject headings:
Caligula, Emperor of Rome, 12-41.
Emperors--Rome--Biography.
Rome--History--Caligula, 37-41.
Harvard subject headings:
Caligula, Emperor of Rome, 12-41.
Emperors--Rome--Biography
Rome--History--Caligula, 37-41.
Rome--History--Tiberius, 14-37
Princeton subject headings: