1Gass,S.M.& Selinker,L Second Language Acquisition:An Introductory Course.London:Lawrence Earlhaum.2001.
2Krashen,S.D.The Input Hypothesis.London:Longman Group Limited.1985.
3Swain,M.Three Functions of Output in Second Language Learning[C]//G.Cook& B.Seidlhofer.Principle and Practice in Applied Linguistics.Oxford:Oxford University Press.1995.
4Donato, R. Collective scaffolding in second language learning [A].J. Lantolf & G. Appel, Vygotskian approaches to second language research [C]. Norwood, NJ: Ablex, 1994.
5Gass, S. & L. Sellinker. Second language acquisition: An introductory course [M]. Mahawah, NJ: Lawrence Erlbaum Associates,2001.
6Izumi, S., Bigelow, M., Fujiwara, M. & Fearnow, S. Testingthe output hypothesis: Effects of output on noticing and second language acquisition. Studies in Second Language Acquisition, 1999(21): 421-452.
7LaPierre, D. Language output in a cooperative learning setting:Determining its effects on second language learning[D]. MA thesis, University of Toronto, Canada, 1994.
8Lightbown, P. & R. Halter. Comprehension-based ESL program in New Brunswick: Grade 8[Z]. Final report to the Department of the Secretary of State, Ottawa, 1993.
9Mackey, A., S. Gass & K. McDonough. Learners' perceptions about feedback [J]. Studies in Second Language Acquisition, 2000(22): 471 - 497.
10Pica, T., Halliday, L., Lewis, N. & Morgenthaler, L. Comprehensible output as an outcome of linguistic demands on the learner[J]. Studies in Second Language Acquisition, 1989(11): 63 - 90.
