3Krashen,D. ( 1987 ) Principles and Practices in Second Language Acquisition. New York : Prentice Hall, 21 - 25.
4Miller,G. A. (1956) The magical number sev- en, plus or minus Two: Some limits on our capacity for processing information. Psychological Review, 63 ( 2 ) : 8l - 97.
5Swain, M. ( 1985 ) Communicative compe- tence: Some roles of comprehensible input and compre- hensible output in its development. In S. M. Gass & C. G. Madden ( Eds. ) , Input in Second Language Acquisi- tion. Rowley, MA: Newbury House, 235 -253.
