1Bialystok, E. Communication Strategies : A Psychological Analysis of SeeondLanguage Use. Oxford: Blaekwell, 1990.
2Krashen. S. The Input Hypothesis : Issues and Implica- tions. London: Longraan,1985.
3Krashen. S. & T. Ten'ell. , The Natural Approach: Language Acquisition in the Classroom[ M]. Oxford: Pergamon, 1983.
4Swaln, M. & S. Lapkin. "Problems in output and the cog- nltive processes they generate: a step towards second language learning". Toronto: Modern Language Center, OISE.