Frederick Douglass, George L. Ruffin (2001). “Life and Times of Frederick Douglass: His Early Life as a Slave, His Escape from Bondage, and His Complete History to the Present Time”, p.61, Digital Scanning Inc
Socrates, Plato, Aristotle (1967). “Wit and Wisdom of Socrates, Plato, Aristotle: Being a Treasury of Thousands of Glorious, Inspiring and Imperishable Thoughts, Views and Observations of the Three Great Greek Philosophers, Classified Under about Four Hundred Subjects for Comparative Study”