1Ellis, N. 2002. Frequency effects in language process- ing:A review with implications for theories of implicit and ex- plicit language acquisition[J].Studies in Second Language Acquisition, 24:143-188.
2Kennedy,G. 1998. An Introduction to Corpus Linguis- tics [M]. London: Addison Wesley Longman.
3Koprowski,M. 2005. Investigating the usefulness of lexical phrases in contemporary coursebooks [J]. ELT Journal 59: 322-332.