4Hutchinson, T. and Waters, A. English For Specific Purposes: A Learning-centred Approach [M]. Cambridge: Cambridge University Press. 1993:21,55
5Widdowson, H.G. EST in theory and practice [A]. In H. G. Widdowson (ed.). Explorations in Applied Linguistics [C]: London: Oxford University Press. 1979 : ;326
6Nunan, D. Designing Tasks for the Comunicative Classroom [M]. Cambridge: Cambridge University Press. 1989:16
7Nunan, D. The Learner-Centred Curriculum-A study in second language teaching [M], Cambridage: Cambridge University Press. 1997:11,44