Author/Authors :
Xiu Xin، Xiu Xin نويسنده Department of Mathematics, Tianjin University of Technology, Tianjin, 300384, P.R.China , , Fu-Gui Shi، Fu-Gui Shi نويسنده Fu-Gui Shi, Fu-Gui Shi , Sheng-Gang Li، Sheng-Gang Li نويسنده College of Mathematics and Information Science, Shaanxi Normal University, 710062, Xian, P. R. China Sheng-Gang Li, Sheng-Gang Li