1. Department of Mathematics, Aarhus University, Aarhus C, Denmark
2. CogniGron (Groningen Cognitive Systems and Materials Center), University of Groningen (UnivGroningen), Groningen, Netherlands
3. Technische Universität Braunschweig, Universitätsplatz 2, Braunschweig, Germany
4. Weierstrass Institute for Applied Analysis and Stochastics, Berlin, Germany
5. Orange SA, Châtillon, France