Concept of Law, The 3rd Revised edition
Paperback by Hart, HLA (late Professor of Jurisprudence, Principal of Brasenose College, and Fellow of University College, University of Oxford); Green, Leslie (Professor of the Philosophy of Law, University of Oxford); Raz, Joseph (Research Professor, University of Oxford and Research Professor, Columbia University Law School); Bulloch, Penelope A. (Balliol College, University of Oxford)