2Arnold ,J. 1999. Affect in Language Learning[ M]. Cambridge:Cambridge University Press.
3Brown, H. 2002. Principle of Language Learning and Teaching [ M ]. Beijing: Foreign Language Teaching and Research Press.
4Lantolf, J. 2000. Sociocultural Theory and Second Language Acquisition [M]. Oxford: Oxford University Press.
5Nunan, D, 2011. Task-based Language Teaching[ M]. Cambridge :Cambridge University Press.
6Richards, J. & T. Rodgers. 2001. Approaches and Methods in Language Teaching [ M ]. Cambridge: Cam- bridge University Press.
7Swain, M. 1985. Communicative competence:Some roles of comprehensible input and comprehensible output in its development[ A]. In S. Gass & C. Madden ( eds. ). Input in Second Language Acquisition [ C ]. Row- ley: Newbury House.
