Affiliation: | 1. Department of Mathematics and Applications, University of Naples Federico II, via Cintia, I-80126 Naples, Italy;2. Department of Electrical and Information Engineering, University of Cassino and Southern Lazio, Via di Biasio 43, I-03043 Cassino, Italy;3. Unidad Académica de Matemáticas, Universidad Autónoma de Guerrero, Av. Lázaro Cárdenas C.U., Chilpancingo, Guerrero, Mexico |