3Brown, H. D. Principles of Language Learning and Teaching [ M ].New Jersey: Prentice-Hall, Inc., 1987.
4Ellis, R. Understanding Second Language Acquisition [M]. Oxford:Oxford University Press, 1985.
5Freeman, D. L and M. H. L on g. An Introduction to Second Language Acquisition [M]. London: Longman Group UK Limited, 1991.
6Lenneberg, E. Biological Foundations of Language [M]. New York:Wiley and Sons, 1967.
7Seliger, H. Implications of multiple critical periods hypothesis for second language learning [ A ]. In Ritchie, W. ( ed. ). Second Language acquisition research [ C]. New Yonk: Academic Press,1978.
8Vandergrift, Larry. Facilitating second language listening comprehension:acquiring successful strategies[J]. ELT Journal, 1999, (53): 168 -175.
