1. Yue-Wu Li:
School of Mathematics and Statistics, Henan University,,China
2. Muhammet Cihat Dagli:
Department of Mathematics, Akdeniz University,Antalya 07058,Turkey
3. Feng Qi:
School of Mathematical Sciences, Tiangong University, Tianjin 300387, China
Institute of Mathematics, Henan Polytechnic University, Jiaozuo 454010, Henan, China