1Asher, J., & Garcia. R. (1969). The optimal age to learn a foreign language. Modem Language Journal, 53, 334 -341.
2Bates, E. (1993) Comprehension and production in early language development. Monographs of the Society for research in child development,58(3 - 4,Serial No.233)
3Cook, V. (1996). Second language learning and language teaching (second edition)(1996),by Arnold, a Member of Hodden Headline Group.
4Curtiss, S. (1977). Genie: A psycholinguistic study of a modem - day"wild child". New York:Academic Press.
5Elman, J.L.(1993). Learning and development in neural networks:the importance of starting small. Cognition, 48,71 -99.
7Grimshaw, G.M., Adelstein, A., Bryden, M.P., & MacKinnon, G.E., (1998). First- language acquisition in adolettuce: evidence for a critical period for verbal language development. Brain and Language 63,237 - 255
8Harley, B.(1986). Age in second language acquisition.Devedon:Multilingual matters. -Allen, P., Cummins, J., and Swain, M. (Eds):The development of second language proficiency. Cambridge University Press.
9Johnson J., & Newport E.(1989). Critical period effects in second language learning :the influence of maturational state on the acquisition of English as a second language. Cognitive Psychology, 21,60-99.
10Kim, K.H.S., Relkin, N.R., Lee, K.M., &Hirsch, J. (1997)Distinct cortical areas associated with native and second languages. Nathure, 388(6638) :171 - 174.
