1. 1. HLA Hart.,The Concept of Law. (Oxford University Press Publication)
   2. Lon L Fuller.,The Morality of Law. (Universal Law Publishing)
   3. George Whitecross Paton., A textbook of jurisprudence. (Clarendon press)
   4. John Finnis., Natural Law and Natural Rights. (Oxford university press)
   5. Richard A. Posner., The Problems of Jurisprudence. (Harvard University press)