1. Department of Exact Sciences, University of S ao Paulo, Piracicaba, Brazil
2. Academic Department of Mathematics, Federal University of Technology – Paraná, Londrina, Brazil
3. Department Exact Sciences, University of São Paulo, Piracicaba, Brazil
4. Department of Statistics, Federal University of Pernambuco, Recife, Brazil
5. Department of Statistics, University of São Paulo, São Carlos, Brazil
6. Department of Statistics, University of Brasilia, Brasilia, Brazil