1. School of Arts and Sciences, Suqian University, Suqian, Jiangsu 223800, P. R. China
2. School of Mathematics and Computer Science, Gannan Normal University, Ganzhou, Jiangxi 341000, P. R. China
3. Department CPST, National Higher School of Technology and Engineering, Annaba 23005, Algeria
4. Department of Mathematics, Taibah University, Al-Medina, Saudi Arabia
5. Laboratory of Analysis and Control of Differential Equations, Faculty MISM, Department of Mathematics, University of 8 May 1945 Guelma, P. O. Box 401, 24000 Guelma, Algeria