6Ellis, R. 1985. Understanding Second Language Acquisition [M]. Oxford: Oxford University Press.
7Ellis, R. 1997. Second Language Acquisition [M]. Oxford: Oxford University Press.
8Granger, S. 1999. A bird's eye view of computer learner corpus research [P]. Paper presented at the second Symposium of Learner English Corpus, Hongkong.
9Laufer, B. 1998. The development of passive and active vocabulary in a second language: Same or different?[J] Applied Linguistics 19/2: 255-271.
