Institution: | (1) MIP, Departement de Mathematique, Universite Paul Sabatier, 31062 Toulouse cedex 04, France;(2) Departamento de Matematica Aplicada, Universidade Federal de Rio de Janeiro, Caixa Postal 68530, CEP 21945-970, Rio de Janeiro, RJ, Brazil;(3) Department of Mathematics, University of Toronto, 100 St. George Street, Toronto, Ontario M5S 3G3, Canada |