Benjamin Franklin, Ulysses S Grant, Andrew Carnegie, Henry Adams (2016). “Great American Lives: The Autobiography of Benjamin Franklin, Personal Memoirs of Ulysses S. Grant, Autobiography of Andrew Carnegie, and The Education of Henry Adams”, p.1082, Open Road Media
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.28