1Ehrich, E. 1987. The generation of tense [A]. In G.Kempen ( ed. ). Natural Language Generation:New Results in Artificial Intelligence, Psychology and Linguistics. Dordrecht: Martinus Nijhlff Publishers.
2Halliday, M. A. K. 1976. The English verbal group[A]. InG. R. Kress (ed.). Halliday: System and Function in Language [C]. Oxford: Oxford University Press.
3Halliday, M.A.K. 1978. Language as Social Semiotic:The Social Interpretation of Language and Meaning[M]. London: Edward Arnold.
4Halliday, M. A. K. 1985/1994. An Introduction to Functional Grammar [ M ]. London: Edward Arnold.
5Halliday, M. A.K. & R. Hasan. 1976. Cohesion in English [M]. London: Longman.
6Hornstein, N. 1977. Towards a theory of tense [J].Linguistic Inquiry 8: 521-58.
7Huddleston, R. 1984. Introduction to the Grammar of English [M]. Cambridge: Cambridge University Press.
8Joos, M. 1964. The English Verb [M]. Madison: University of Wisconsin Press.
9Lyons, J. 1968. Introduction to Theoretical Linguistics[M]. New York: Cambridge University Press.
10Martin, J.R. 1992. English Text : System and Structure [M]. Amsterdam: Benjamins.
