1Austin.J.L. 1962. How to Do Things with Words. Oxford: Clarendon Press.
2Chomsky.N. 1965. Aspects of the Theory of Syntax. Cambridge, Mass. : MIT Press.
3Chomsky,N. 1980. "On cognitive structures and their development: a reply to Piaget" in M. Piatelli-Palmarini (ed.). Language and Learning. London: Routledge and Kegan Paul.
4Ellis. R. 1985. Understanding Second Language Acquisition. Oxford University Press.
5Krashen. S. 1981. Second Language Acquisition and Second Language Learning. Oxford: Pergamon.
6Krashen,S. 1982, Principles and practice in Second Language Acquisition. Oxford : Pergamon.
7Littlewood.W. 1979. "Communicative performance in language developmental contexts", International Review, of Applied Linguistics XVII: 123-38.
8Vygotsky, L. 1962. Thought and Language. Cambridge. Mass.: MIT Press.