7Biber, D. 1998. Variation Across Speech and Writing[M]. Cambridge: CUP.
8Connor, U. 1995. Examining syntactic variation across three English-speaking nationalities through a multifeature/multi-dimensional approach [A]. In D. L.Rubin (ed.). Composing Social Identity in Written Language [ C]. Hillsdale, N. J.: Lawrence Erlbanm.
9Dantas-Whitney, M. & W. Grabe. 1989. A comparison of Portuguese and English newspaper editorials [A].Paper presented at the 23rd Annual TFSOL Convention, San Antonio, Texas, 1989.
10Ferris, D. F. 1994. Rhetorical strategies in student persuasive writing: Differences between native and nonnative English speakers [J ]. Research in the Teaching of English 28: 45-63.
