8[1]Krashen,S.Second Language Acquisition and Second Language Learning[M].Oxfrod:Pergamon Press,1982.
9[2]Swain,M.Communicative competence:Some role s of comprehensible input and comprehensible output in its development[A].S.Gass &C.Madden,Input in second language acquisition[C].Rowley,MA:Newbury House,1985.
10[3]Swain,M.Three functions of output in second language learning[A].G.Cook &B.Seidlhofer,Principle and Practice in Applied Linguistics[C].Oxford,England:Oxford University Press.1995.