Institution: | 1. Dipartimento di Matematica “G. Castelnuovo”, Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy;2. Center for Mathematical Analysis, Geometry, and Dynamical Systems, Departamento de Matemática, Instituto Superior Técnico, 1049-001 Lisboa, Portugal;1. Center for General Education, National Quemoy University, Kinmen, Taiwan 892, ROC;2. Department of Mathematics and Information Education, National Taipei University of Education, Taipei, Taiwan 106, ROC |