Francis Bacon (1866). “The Moral and Historical Works of Lord Bacon: Including His Essays, Apophthegms, Wisdom of the Ancients, New Atlantis, and Life of Henry the Seventh”, p.191
Adam Smith (1843). “An Inquiry Into the Nature and Causes of the Wealth of Nations With a Life of the Author: Also a View of the Doctrine of Smith, Compared with that of the French Economists, with a Method of Facilitating the Study of His Works, from the French of M. Jariner”, p.177
John Locke, Ruth Weissbourd Grant, Nathan Tarcov (1996). “Some Thoughts Concerning Education: And, Of the Conduct of the Understanding”, Hackett Publishing