1. School of Mathematical Sciences, Laboratory of Mathematics and Complex Systems, Beijing Normal University, Beijing 100875, P. R. China
2. Moscow Center for Fundamental and Applied Mathematics, Moscow State University, Moscow, Russia
3. Moscow Institute of Physics and Technology, Moscow 105005, Russia
4. Northeastern University, Shenyang City, Liaoning Province, People’s Republic of China
5. Kazan Federal University, Kazan, Russia
6. College of Mathematics and Statistics, Guangxi Normal University Guilin 541004, P. R. China