1. Richard T. Ely,Monopolies and Trusts (New York: MacMillan, 1990), p. 162.
2. John Bates Clark and Franklin Giddings,Modern Distributive Processes (Boston: Ginn & Co., 1888), p. 21.
3. Herbert Davenport,The Economics of Enterprise (New York: MacMillan, 1919), p. 483.
4. James L. Laughlin,The Elements of Political Economy (New York: American Book, 1902), p. 71.
5. Irving Fisher,Elementary Principles of Economics (New York: MacMillan, 1912), p. 330.