Affiliation: | 1. Department of Mathematics, National Central University, Chung-Li 320, Taiwan, ROC;2. Department of Applied Mathematics, National Chiao-Tung University, Hsin-Chu 300, Taiwan, ROC;1. Dipartimento di Matematica, Università di Pisa, Largo Bruno Pontecorvo 5, 56127 Pisa, Italy;2. Fakultät für Mathematik, Otto-von-Guericke-Universität, Postfach 4120, 39016 Magdeburg, Germany |