Cita APA (7th ed.)

Broughton, G. (1990). Penguin English grammar A-Z exercises. Penguin Group.

Cita Chicago (17th ed.)

Broughton, Geoffrey. Penguin English Grammar A-Z Exercises. London: Penguin Group, 1990.

Cita MLA (9th ed.)

Broughton, Geoffrey. Penguin English Grammar A-Z Exercises. Penguin Group, 1990.