April 1992 - December 1994: Research and Teaching Fellow of Prof. Dr. G. Gornig at the Institute for International Law, University of Göttingen/Germany. Research in European administrative law.
November 1990 - March 1992: Research and Teaching Fellow of Prof. Dr. V. Götz, University of Göttingen. EU/EU citizenship law, administrative law.
November/December 1988: Student research assistant (Studentische Hilfskraft) of Prof. Dr. V. Götz.