Cita APA (7a ed.)

Duckworth, M., & Gude, K. (2001). Countdown: To first certificate. Oxford University Press.

Cita Chicago Style (17a ed.)

Duckworth, Michael, y Kathy Gude. Countdown: To First Certificate. Oxford: Oxford University Press, 2001.

Cita MLA (9a ed.)

Duckworth, Michael, y Kathy Gude. Countdown: To First Certificate. Oxford University Press, 2001.