Joseph Butler, Stephen L. Darwall (1983). “Five Sermons, Preached at the Rolls Chapel and A Dissertation Upon the Nature of Virtue”, p.47, Hackett Publishing
Joseph Butler (1856). “The analogy of religion, natural and revealed, to the constitution and course of nature: to which are added, two brief dissertations : On personal identity, and On the nature of virtue; and fifteen sermons”, p.432
M. Scott Peck (2002). “The Road Less Traveled, 25th Anniversary Edition: A New Psychology of Love, Traditional Values, and Spiritual Growth”, p.83, Simon and Schuster
Austin Osman Spare (2007). “The Writings of Austin Osman Spare: Anathema of Zos, the Book of Pleasure and the Focus of Life”, p.18, Filiquarian Publishing, LLC.