APA aipamena

Duckworth, M. (1999). Countdown to first certificate. Oxford: Oxford University Press.

Chicago Style aipamena

Duckworth, Michael. Countdown to First Certificate. Oxford: Oxford University Press, 1999.

MLA aipamena

Duckworth, Michael. Countdown to First Certificate. Oxford: Oxford University Press, 1999.

Kontuz: berrikusi erreferentzia hauek erabili aurretik.