Institution: | 1 System Engineering and Computer Science Program UFRJ Mailbox 68511, zipcode 21945-970 Rio de Janeiro, Brazil. E-mail: vaniac{at}cos.ufrj.br, 2 System Engineering and Computer Science Program and Mathematics Institute UFRJ Mailbox 68511, zipcode 21945-970 Rio de Janeiro, Brazil. E-mail: mario{at}cos.ufrj.br |