4Wehens, B. The Attrition of Foreign--Language Skills: A Literature Review[J]. Applied Linguistics 8. 1987.
5Nelson, T. Detecting small amounts of information in nemory : savings for non - recognized items [ J ]. Journal of Experimental Psychology: Human Learning and Memory, [978, (5) : 453 -468.
6Bahriek, H. Fifty years of second language attrition: Impli- cations for programmatic research [ J ]. Modem Language Journal , 1984 , 68:105 -118.
7Cummins, J. Linguistics interdependence and the educa- tional development of bilingual children[ J ]. Review of Ed- ucational Research, 1979.
