1White, L. The "Pro-drop" parameter in adult second language acquisition[J]. Language Learning, 1985, (35): 47-62.
2Lakshmanan, U. The role of parametric variation in adult second language acquisition: A study of the "pro-drop" parameter[J]. Papers in Applied Linguistics. Michigan: Ann Arbor, 1986,(2):97-118.
3Gass, S. & J. Ard. L2 acquisition and the ontology of language universals[A]. W. Rutherford. Language Universals and Second Language Acquisition[C]. Amsterdam: John Benjamins, 1984. 33-68.
4Gass, S. Universals, SLA and language pedagogy: 1984 re-visited[A]. L. Eubank,, L. Selinker & M. Sharwood Smith. The Current State of Interlanguage[C]. Amsterdam: John Benjamins, 1995. 31-42.
5Rumelhart, D. & J. McMelland. On learning the past tense of English verbs[A]. J. McClelland & D. Rumelhart. Parallel Distributed Processing: explorations in the microstructure of cognition. Vol.2: Psychological and Biological Models[C]. Cambridge, MA: MIT Press, 1986. 216-71.
6Brown, G., K. Malmkjoer & J. Williams. Performance and Competence in Second Language Acquisition[M]. Cambridge: Cambridge University Press, 1996. 153.
7Ellis, N. C. Analyzing language sequence in the sequence of language acquisition: Some comments on Major and Ioup[J]. Studies in Second Language Acquisition, 1996, (18): 361-8.
8Seidenberg, M. S. Language acquisition and use: Learning and applying probabilistic constraints[J]. Science, 1997, 275:1599-1603.
9Gass, S. & L. Selinker. Second Language Acquisition: An Introductory Course[M]. New Jersey: Lawrence Erlbaum, 1993.92-95.
10Guion, S. G., J. E. Flege, S. H. Liu & G. H. Yeni-Komshian. Age of learning effects on the duration of sentences produced in a second language[J]. Applied Psycholinguistics, 2000,(21):205-228.
