Affiliation: | 1.Institute of Mathematics, University of Campinas, Rua Sergio Buarque de Holanda, 651, Campinas, 13083-859, S?o Paulo, Brazil ;2.Academic Regional Center of Bariloche, National University of Comahue, Quintral 1250, San Carlos de Bariloche, Rio Negro, Argentina ;3.Department of Applied Mathematics, Federal University of Espírito Santo, Rodovia BR 101, Km 60, 29932-540, S?o Mateus, Espírito Santo, Brazil ; |