Upon his retirement from the faculty of University of California at Berkeley in 1952, noted legal philosopher and political scientist Hans Kelsen produced arguably this his most important work, "... a systematic study of the most important aspects of international law, including international delicts and sanctions, reprisals, the spheresof validity and the essential function of international law, creation and application of international law and national law." Nicoletta Bersier Ladavac, "Hans Kelsen (1881 - 1973) Biographical Note and Bibliography," European Journal of International Law Vol. 9 (1998) No. 2.