1Krashen.S.D,Second language Acquisition and Second Language Lear- ningfM].Oxford:Pergamon, 1981.
2Krashen.S.D.Principles and Practice in Second Language Acquisition [M].New York :Pergamon Press,1982.9-32.
3Krashen.S.D.The Input Hyphotheses:Issuss and Implications[M].1985. 9.
4Ellis.R.Understanding Second Language Acquisition [M].OxfortL'Oxford University Press,1985.
5SWAIN.M.Communicative Competene: Some Roles of Comprehensible Input and Comprehensible Output in Its Development [A].Cass S, MaddenC. Input in Second Lansuage Acquisition [C].P, xow ley ,M: New bury House,1985.
2[2]Krashen.S.D.Principles and Practice in Second Langauge Acquisition.New York:Pergamon Press Ltd.,1982.
3[3]Seliker,H.Psycholiguistic Issues in Second Language Acquistion.In L.M.Beebe (ed) Issues in Second Langauge Acquisition:Multiple Perspectives.New York:Newbury House Publishers,1988.
