Adam Smith (2007). “The Wealth of Nations: An Inquiry Into the Nature and Causes of the Wealth of Nations: With an introduction by Jonathan B. Wight, University of Richmond”, p.400, Harriman House Limited
Thomas Paine (1824). “The Political Writings of Thomas Paine: Secretary to the Committee of Foreign Affairs in the American Revolution : to which is Prefixed a Brief Sketch of the Author's Life”, p.410