1. National Engineering Laboratory for Modern Silk, College of Textile and Engineering, Soochow University, Suzhou, P. R. China
2. School of Mathematical Sciences, Soochow University, Suzhou, P. R. China
3. Department of Mathematics, Government College University, Faisalabad, Pakistan
4. School of Mathematics and Information Science, Henan Polytechnic University, Jiaozuo, P. R. China
5. School of Science, Xi’an University of Architecture and Technology, Xi’an, P. R. China