1Dudley-EvansT. & St. John M. J. Developments in English for Specific Purposes [M].Cambridge:Cambridge Uni- versity Press, 1998.
2Hutchinson,T. & Waters A. English for Specific Pur- poses [M].Cambridge: Cambridge University Press, 1987.
3Strevens,P. ESP after Twenty Years: A Re-appraisal . In M. Tickoo(ed.)ESP:State of the Art, Anthology Series 21[C]. Seameo Regional language Center, 1988.4.2.