1. The European Union as an essentially contested project;European Law Journal,1998
2. The European Union?,1996
3. The three levels of citizenship within the European Union;German Law Journal,2014
4. The citizenship in today’s Europe: An interview with Rainer. [Edited by L. G. Baglioni];Società Mutamento Politica,2016
5. Building the union: The nature of sovereignty in the political architecture of Europe;Law and Philosophy,1997