1. Institute of Mathematics, Statistics and Scientific Computation University of Campinas—UNICAMP, Rua Sérgio Buarque de Holanda 651, 13083-859 Campinas, SP, Brazil
2. Department of Statistics Federal University of Pernambuco—UFPE, Av. Prof. Luiz Freire S/N, 50740-540 Recife, PE, Brazil