8Nation, I. S. P. Teaching and Learning Vocabulary [M]. Massa- chusetts: Newbury House, 1990.
9Mackey, W. F. and J. G. Savard. The Indices of Coverage[J]. IRAL, 1967 (5).
10Nagy, W. E. , Anderson, R. C. , Schommer, M. , Scott, J. A. and A. Stallmam. Morphological Families in the Internal Lexicon [J]. Reading Research Quarterly, 1989 (4).