5[1]Bachman,Lyle F.Fundamental Considerations in Language Testing[M].Oxford:Oxford University Press,1990.
6[2]Dulay,H.,Burt,M.and Krashen,S.Language Two[M].Oxford:Oxford University Press,1982.
7[3]Freed,B.F.Language loss:Current thoughts and future directions[A].InR.D.Lambert & B.F.Freed (eds.),The loss of language skills[C].Rowley,MA:Newbury House,1982.
8[4]Tomiyama,M.A longitudinal study of L 2 attrition-The initial stage[A].In L.Hansen (ed.),Second Language Attrition in Japanese Contexts[C].Oxford:Oxford University Press,1999.
9[5]Van Els,T.An overview of European research on language acquisition[A].In B.Weltens,K de Bot,and T.Van Els (eds.),Language Attrition in Progress ICl.Dordrecht:Foris Publications,1986.
10[6]Weltens,B.The Attrition of Foreign-Language Skills:A Literature Review[J].Applied Linguistics,1987,(1):22 -36.
