1 AGIM Laboratory, FRE 3405 UJF-CNRS, TIMB Team, University J. Fourier of Grenoble (UJF), Faculty of Medicine, 38700 La Tronche
2 Laboratoire de Mathématiques, CNRS et Université de Paris-Sud XI, F-91405 Orsay Cedex
3 Graduate school of Mathematical Sciences, University of Tokyo, Komaba 3-8-1, Tokyo 153-8914
4 Department of Mathematics, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tamaku, Kawasaki 214-8571