1. Department of Mathematics, Guizhou University, Guiyang, Guizhou 550025, P. R. China
2. Department of Mathematics and Sciences, Prince Sultan University, P. O. Box 66833, 11586 Riyadh, Saudi Arabia
3. Department of Medical Research, China Medical University, Taichung 40402, Taiwan
4. CONACyT-Tecnológico Nacional de México/CENIDET, Interior Internado Palmira S/N, Col. Palmira, C.P. 62490, Cuernavaca, Morelos, México
5. Consejo Académico, Universidad Virtual CNCI, Monterrey, México
6. School of Automation, Northwestern Polytechnical University, 170072 Xian, P. R. China