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”
John D. Rockefeller (2015). “John D. Rockefeller on Making Money: Advice and Words of Wisdom on Building and Sharing Wealth”, p.16, Skyhorse Publishing, Inc.