Cita APA (7a ed.)

Duckworth M. Michael & Gude K. Kathy. (2004). Countdown to First Certificate: Student's book. Oxford, Oxford University Press, 2004.

Cita Chicago Style (17a ed.)

Duckworth M. Michael y Gude K. Kathy. Countdown to First Certificate: Student's Book. Oxford, Oxford University Press, 2004, 2004.

Cita MLA (9a ed.)

Duckworth M. Michael y Gude K. Kathy. Countdown to First Certificate: Student's Book. Oxford, Oxford University Press, 2004, 2004.