4Ellis, R. The Study of Second Language Acquistion[M].Oxford University Press, 1997.
5Chaudron, C. Foreigner-talk in the clasroom - an aid to learning?[A].Seliger, H. and M. Long (eds.). Classroom oriented research in second language acquisition[C]. Rowley, Mass. : Newbury House,1983.
6Gaies, S. The nature of linguistic input in formal second language learning: linguistic and communicative Strategies [A]. H. Brown, C. Yorio and R. Crymes ( eds. ) . On TesoL '77 [C]. Washington D.C.:TESOL, 1977.
7Gaies, S. Linguisitic input in first and second.language learning [A].F. Eckman and A.Hastings (eds.). Studies in first and second language acquisition [C]. Rwoley, Mass.: Newbury House, 1979.
