ZHU Hui-ming
College of Business Administration, Hunan University, Changsha 410082, China;LI Su-fang
College of Business Administration, Hunan University, Changsha 410083, China;ZENG Hui-fang
College of Business Administration, Hunan University, Changsha 410084, China;YU Ke-ming
Department of Mathematics, Brunel University, London UB8 3PH, UK