1Freed,B. F. Language loss:Current thoughts and future directions [A]. R. D. Lambert & B. F. Freed. The Loss of Language Skills [C]. Rowley, MA: Newbury House Publishers, 1982 : 1 - 5.
2Edwards,G. Second Language Retention in the Public Service of Canada [C]. Ottawa:Public Service Commission of Canada, 1977.
3Burling, R. Language development of a Garo-and English- speaking child[A]. E. Hatch. Second Language Acquisition [C]. Rowley, MA : Newbury House, 1978 : 54- 75.
4Nagasawa,S. Learning and losing Japanese as a second language:A multiple case study of American university students[A]. L. Hansen. Second Language Attrition in Japanese Contexts [C]. Oxford: Oxford University Press, 1999 : 169- 199.
5Hansen, L. & A. Reetz-Kurashige. Investigating second language attrition: An introduction [A]. L. Hansen. Second Language Attrition in Japanese Contexts [C]. Oxford : Oxford University Press, 1999 : 3- 20.
