Duckworth, M. (2009). Countdown to first certificate. Oxford: Oxford University Press.
Trích dẫn kiểu ChicagoDuckworth, Michael. Countdown to First Certificate. Oxford: Oxford University Press, 2009.
MLA引文Duckworth, Michael. Countdown to First Certificate. Oxford: Oxford University Press, 2009.
警告：這些引文格式不一定是100％准確.