Affiliation: | 1. College of Mathematics and Statistics, Taishan University, Taian, 271021, China;2. Department of Mathematics, Hohai University, Nanjing, China;1. Department of Mathematics, Larbi Ben M’Hidi University, Oum El Bouaghi 04000, Algeria;2. ETS Ingenieros industriales, Universidad de Salamanca, Bejar E37700, Spain |