| Affiliation: | 1. Dipartimento di Matematica e Informatica, Università degli studi di Perugia, Perugia, Italy;2. Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università degli Studi di Modena e Reggio Emilia, Modena, Italy;1. Department of Mathematics and Computer Science, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada;2. Department of Mathematics, National Defense Academy of Japan, Yokosuka, Kanagawa 239-8686, Japan;1. School of Science, Chang''an University, Xi''an 710064, China;2. School of Information Engineering, Chang''an University, Xi''an 710064, China |
