Professor of International Tax Law at the University of Leiden (The Netherlands), Chairman of the International Tax Center Leiden and Director of the Leiden Adv LL.M. Program in International Tax Law. He is also Chairman of the Board of the Association of European Tax Professors (until June 2012) and Deputy Judge in the Tax Chamber of a Court of Appeal in the Netherlands. In addition to his professorship in Leiden, member of the Global Law Faculty of New York University and a Permanent Visiting Professor at Peking University in Beijing, China. Visiting professor at various foreign law and business schools: University of Florida, USA (1982, 1997, 2003), Universities of Stockholm and Uppsala, Sweden (1987), University of London, UK (1990), Emory University, USA (1991), Bocconi University, Italy (1993, 1994, 2002), University of California (Hastings College of the Law), USA (1996, 2008), the Free University of Brussels (1997), University of Sydney, Australia (1998, 2005, 2010), Xiamen University, China (2004), Georgetown University, USA (2011).