MLA

Swan, Michael, and Catherine Walter. How English Works : a Grammar Practice Book with Answers. 3rd. imp. Oxford: University Press, 1997.

APA

Swan, M., & Walter, C. (1997). How English works : a grammar practice book with answers. 3rd. imp. Oxford: University Press.

Chicago

Swan, Michael, and Catherine Walter. How English Works: A Grammar Practice Book with Answers. 3rd. imp. Oxford: University Press, 1997.