Plutarch’s Lives; Froude’s Cæsar; Shakspeare’s Antony and Cleopatra; Plato’s Dialogues; Horace, Martial, and Juvenal, especially among the poets; Lord’s Old Roman World; Suetonius’s Lives of the Cæsars; Dion Cassius; Rollins’s Ancient History; Merivale’s History of the Romans; Biographic Universelle; Rees’s Encyclopedia has a good article.