1Douglas, W. 1966. On teaching the process of writing [A]. In A. Frazier (Ed.), New Directions in Elementary English [C]. Urbana, Ⅲ.: National Council of Teachers of English. 184-186.
2Krashen, S. D. 1985. The Input Hypothesis: Issues and Implications [M]. London: Longman.
3Tribble, C. 1996. Writing [M]. Oxford: Oxford University Press.
