5Beebe, L. T., Takahashi & R. UIiss-Weltz. Pragmatic transfer in ESL refusals [A]. In R. Scarcella, E. Anderson & S. D.Krashen ( eds. ) . On the Development of Communicative Competence in a Second Language [ C ]. Cambridge, MA: Newbury House. 1989.
6Ellis,R.The Study of Second Language[M].上海:上海外语教育出版社,2000.