Many thanks to my Chinese teachers :
Wang Xindan, Kunming Normal University Zhang Ling, Nanjing Normal University
Yuan Mei, Yang Yan, Li Ying, Qufu Normal University
Pan Guini, Dai Yinfeng, Guo Yu, Liu Yunjing, Tao Shanshan, Fang Xiaobei, Shanghai Donghua University
Zhang Yan, Xi'an Jiaotong University
