5[4]Biber,D. ,S. Johnson,G. Leech,S. Conrad,& E,Finegan, Longman Grammar of Spoken and Written English [M]. London: Longman, 1999.
6[5]Greenbaum, Sidney. Oxford English Grammar [M].Oxford University Press, 1996.
7[6]Granger,Sylviane. Learner English on Computer[M].Longman, 1998.
8[7]Hann,d. Pieter. An Introduction to Corpus Linguistics [M]. Longman, 1998.
9[8]Kennedy,Graeme. An Introduction to Corpus Linguistics[M]. Longman, 1998.
10[9]Nelson,Gerald. A Study of the Top 100 Wordforms in ICE-GB Text Categories[J]. International Journal of Lexicography, Vol. 10 No. 2. Oxford : Oxford University Press, pp112- 134.