1996-1997
Campinas, SP, Brazil: At the 1996 WORKSHOP on Orthogonal Functions, Moment Theory, Padé Appro-ximants and Applications  Campinas, SP, Brazil: At the 1996 WORKSHOP on Orthogonal Functions, Moment Theory, Padé Appro-ximants and Applications 
Goiânia, GO, Brazil:  At the XIX Congresso Nacionalde Matemática Aplicada e Computacional.    Gramado, RS, Brazil:  At the XX Congresso Nacionalde Matemática Aplicada e Computacional.