First Author:   Luiz A. Esteves Federal University of Paraná and University of Siena esteves@ufpr.br   Avenida Celso Garcia 5885, bloco 2 apto. 51 Bairro Tatuapé São Paulo, 03063-000, Brazil   005511-61930627(Phone) 005511-61930627(Fax) http://www.sitenarede.com/luiz_esteves/