1Krashen - The Input Hypothesis [M]. London: Longman, 1985: 175.
2Swain M. Communicative Competence : Some Roles of Comprehensible Input and Comprehensible Output in Its Development [M] // S Gass, C Madden . Input in Second Language Acquisition. Rowley, MA:Newburry House, 1985: 235--253.
3Krashen, S. The Input Hypothesis[M].London:Longman,1985.
4Swain, M. Communicative competence:Some roles of comprehensible input and comprehensible output in its development[A].Rowley,Mass:Newbury House,1985.235-253.