 Other positions have included Director and Founder of the Institute of Anglo-American Law, Leiden, member of the Council of Management of the British Institute of International and Comparative Law, member of the Board of Management of the Institute of Advanced Legal Studies, member of the Board of Editors of "European Review of Private Law", "Revue de droit internationale et de droit comparé", and "The Netherlands Journal of International Law".He has held visiting professorships at Cornell Law School, University of Paris I, Panthéon-Assas University, the University of Michigan Law School, the University of Ghent, and the University of Siena.He has authored or co-authored thirty books and more than one hundred and twenty articles in languages including English, French, German, and Greek.