9Davies, A. 1991. The Native Speaker in Applied Linguistics [ M ]. Ed- inburgh : Edinburgh University Press.
10Grabe, W. & F. Stoller. 1997. Content-based instruction: Research foundations[ A]. In M. Snow & D. Brinton ( eds. ). The Content- based Classroom:Perspectives on Integrating Language and Content [ C ]. New York: Longman.