Thomas Jefferson (2010). “The Works of Thomas Jefferson: Correspondence 1771 - 1779, the Summary View, and the Declaration of Independence”, p.212, Cosimo, Inc.
Aristotle, (2016). “Aristotle's Politics: Writings from the Complete Works: Politics, Economics, Constitution of Athens”, p.69, Princeton University Press
Speaking to the Roman Senate, as recorded by Sallust in The Catiline War (c. 40 b.c.). This quotation is a favorite of CIA counterintelligence officers.