1Hu,M. & Nation,P. (2000) Unknown vocabulary density and reading comprehension. Reading in a Foreign Language ,13(1) : 403 - 430.
2Laufer,B. ( 1989) What percentage of text-lex-is is essential for comprehension. In C. Lauren & M. Nordman ( eds. ),Special Language : From Humans Thinking To Thinking Machines. Clevedon : Multilingual Matters, 316-323.
3Nattinger,J. R. & DeCarrico,J. S. (1992) Lexical Phrases and Language Teaching. Oxford : Oxford University Press.
4Swain, M. (2000) The output hypothesis and beyond : Mediating acquisition through collaborative dialogue. In J. P. Lantolf ( ed. ) , Sociocultural Theory and Second Language Learning. Oxford : Oxford University Press,97 - 114.