Halliday, M. A. (1985). An Intruduction to Functional Grammar. London: Edward Arnold.
Leech, G. and Svartvik, J. (2000). A Communicative Grammar of English. London: Longman.
Quirk, R., Greenbaum, S., Leech, G., and Svartvik, J. (1985). A Contemporary Grammar of The English Language. U.S.A: Longman.