MLA

Leech, Geoffrey Neil, and Jan Svartvik. A Communicative Grammar of English. 2nd [rev.] ed. London: Longman, 1994.

APA

Leech, G. Neil, & Svartvik, J. (1994). A communicative grammar of English. 2nd [rev.] ed. London: Longman.

Chicago

Leech, Geoffrey Neil, and Jan Svartvik. A Communicative Grammar of English. 2nd [rev.] ed. London: Longman, 1994.