Institution: | 1. Department of Mathematics , Iowa State University , Ames, Iowa, 50011, USA;2. Department of Computer Science , Clemson University , Clemson, SC, 29634-1906, USA;3. Departamento de Matemática , Universidade de Sao Paulo , C.P. 20570 (Ag. Jardim Paulistano), Sao Paulo, 01452-990, Brazil |