5Krashen, S.D.Principles and practice in second language acquisition [M].Oxford: Pergamon.1982.
6Krashen, S.D.The input hypothesis: Issues and implications [M].London: Longman.1985.
7Swain, M.Three functions of output in second language learning [A].In Cook G, Seidlhofer B.(eds.).Principles and Practice in applied Linguistics: Studies in honour of H.G.Widdowson [C].Oxford University Press.1995.
8Long, M.1983.Does instruction make a difference? A review of research [J].TESOL Quarterly 17:359-382.
9Swain, M.The output hypothesis: Just speaking and writing aren't enough [J].The Canadian Modern Language Review.1993,(1):158-164.
10Harmer, J.The Practice of English Language Teaching[M].London: Longman.1983.
