Cita APA (7th ed.)

Walker, M. (1989). ESL: Activity book (1a. ed.). Addison-Wesley.

Cita Chicago (17th ed.)

Walker, Michael. ESL: Activity Book. 1a. ed. Reading: Addison-Wesley, 1989.

Cita MLA (9th ed.)

Walker, Michael. ESL: Activity Book. 1a. ed. Addison-Wesley, 1989.