2Gass,S.& Selinker,L.(Eds.)Language transfers and language learning(revised edition).Amsterdam:John Benjamins,1993.
3James,A.Natural language understanding.London:The Benjamin/Cummings Publishing Com.,1995.
4Richards,J.C.,J.Platt,& H.Platt.Longman dictionary of language teaching & applied linguistics.Beijing:Foreign Language Teaching and Research Press,2000.
5Roach,P.Phonetics.Shanghai:Shanghai Foreign Language Education Press,2003.
6Ellis,R.Second language acquisition.Shanghai:Shanghai Foreign Language Education Press,2000.
