6Allendorff, S. 1980. Wiedererwerb einer Zweitsprache, dargestellt am Bcispiel der Englischen Negation [ D]. PhD Dissertation. Englisches Seminar der Universitat Kiel.
7Bahrick, H. 1984. Fifty years of second language attrition: Implications for programmatic research [J].The Modern Language Journal 68: 105-118.
8Clark, J. &E. Jorden. 1984. A Study of Language Attrition in Former U. S. Students of Japanese and Implications for Design of Curriculum and Teaching Materials. Final Project Report [M]. Washington, DC: Center for Applied Linguistics.
9Cohen, A. 1975. Forgetting a second language [J]. Language Learning 25: 127-138.
10Edwards, G. 1976. Second language retention in the Canadian public service [J]. The Canadian Modern Language Review 32 : 305-308.