George MacDonald (2015). “The Complete Novels of George Macdonald (Illustrated): The Princess and the Goblin, The Princess and Curdie, Phantastes, At the Back of the North Wind, Lilith, David Elginbrod, Malcolm, Ranald Bannerman's Boyhood, Wilfrid Cumbermede and many more”, p.8795, e-artnow
Attributed to Aristotle in Diogenes Laertius "The Lives and Opinions of Eminent Philosophers" translated by C. D. Yonge and Henry G. Bohn (p. 188), 1853.