1. School of Mathematics and Statistics, Key Laboratory of Applied Statistics of MOE, Northeast Normal University, Changchun, Jilin Province, P.R. China;
2. Key Laboratory of Unconventional Oil and Gas Development, China University of Petroleum (East China), Ministry of Education, Qingdao, P.R. China;
3. College of Science, China University of Petroleum, Qingdao, Shandong Province, P.R. China;
4. Nonlinear Analysis and Applied Mathematics (NAAM)-Research Group, King Abdulaziz University, Jeddah, Saudi Arabia;
5. Department of Mathematics, Quaid-i-Azam University, Islamabad, Pakistan