College of Management and Economics Tianjin University No.92 Weijin Road Nankai District Tianjin 300072 China;
College of Management and Economics Tianjin University No.92 Weijin Road Nankai District Tianjin 300072 China;
College of Management and Economics Tianjin University No.92 Weijin Road Nankai District Tianjin 300072 China;
Department of Management and Engineering Link?oping University Link?oping SE-58183 Sweden;