1. 2The Nature and Causes of the Wealth of Nations, R. H. Campbell, and A. S. Skinner , Oxford, Clarendon Press, 1976 , p. 456 . First published 1776.
2. 4H. L. A. Hart , The Concept of Law , Oxford, Clarendon Press, 1961 , pp. 193 -200 .
3. An Introduction to Modern Political Theory