Ernest Holmes, Michael Beckwith (2010). “How to Change Your Life: An Inspirational, Life-Changing Classic from the Ernest Holmes Library”, p.228, Health Communications, Inc.
Marcus Aurelius, Plato, Aristotle (2012). “The Modern Library Collection of Greek and Roman Philosophy 3-Book Bundle: Meditations; Selected Dialogues of Plato; The Basic Works of Aristotle”, p.221, Modern Library