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”
Sylvia Boorstein, Ph.D. (2007). “Pay Attention, for Goodness' Sake: Practicing the Perfections of the Heart--The Buddhist Path of Kindness”, p.23, Ballantine Books