5Swain M. The Output Hypothesis:Just Speaking and Writing Aren' t Enough[ J]. The Canadian Modem Language Review, 1993, ( 1 ) : 158 - 164.
6Swain M. , S. Lapkin, Problems in Output and Cognitive Process They Generate : A step towards second language learning [ J ]. Ap- plied Linguistics, 1995, (6) :371 - 391.
9Krashen S.D.Principles and Practice in second language Acquisition[M] New York:Pergaman Press,1982.
10Swain,M.Communicative competence:some roles of comprehensible input and comprehensible output in its development[A].Gass,S.and Madden,C.Input in second language acquisition[M].Rowley,Mass.:Newbury House,1985.