2Swain M. Three functions of output in second language acquisition [ M]//Cook G, Scidlhofer B. Principles & practice in applied linguistics. Oxford : Oxford University Press, 1995 : 132.
3李维.认知心理学研究[M].杭州:浙江人民出版社,1998..
4Krashen, S. D. The Input Hypothesis: Issues and Implication[M]. London: Longman,1985.
5Krashen, S. D. Language Acquisition and Language Education[M].Oxford Pergamon Press Ltd,1989.
