7Grice, H. P. Logic and conversation [A]. In P. Cole and J. Morgan (eds.). Syntax andsemantics, Vol. 3: Speech acts [C]. New York: Academic Press, 1975:41 --58.
8Ellis R.The Study of Second Language Acquisition[M].Oxford:Oxford University Press,1994.
9Krashen,S.Principles and Practice in Second Language Acquisition[M].Oxford:Pergamon Press,1982.
10Williams,M.& Burden,R.L.Psychology for Language Teachers[M].Cambridge:Cambridge University Press,1997.