Affiliation: | (1) Laboratoire de Topologie, UMR 5584 du CNRS, Université de Bourgogne, BP 47 870, 21078 Cedex Dijon, France;(2) IMPA, Estrada D. Castorina 110, 22460-320 Rio de Janeiro, Brazil;(3) IMPA, Estrada D. Castorina 110, 22460-320 Rio de Janeiro, Brazil;(4) Department of Mathematics, Northwestern University, 2033 Sheridan Road, IL 60208-2730 Evanston, USA |