Institution: | 1.Pennsylvania State University, 483A Business Building, State College, Pennsylvania, 16802, USA ;2.Department of Mathematics, Shanghai University, No. 99, Shangda Road, BaoShan District, Shanghai, 200444, P. R. China ;3.College of Science, China University of Petroleum, No. 66, West Changjiang Road, Huangdao District, Qingdao, 266580, P. R. China ; |