Mark Twain, John Sutton Tuckey (1980). “The Devil's Race-track: Mark Twain's Great Dark Writings : the Best from Which was the Dream? and Fables of Man”, p.337, Univ of California Press
Joseph Butler, Samuel Hallifax (1848). “The works of ... Joseph Butler ... to which is prefixed: an account of the character and writings of the author”, p.196