1Biesenbach-Lucas, S. et al. Use of cohesive features in ESL students' e-mail and word-processed text: a comparative study[J]. In Computer Assisted Language learning, 2000(3 ):211-37.
2Connor, U. Contrastive Rhetoric: Cross-cultural Aspects of Second Language Writing[M]. Cambridge, UK: Cambridge University Press, 1996.
3Halliday, M.A.K. &Hasan, R. Cohesion in English[M]. London: Longrnan, 1976.
