Duckworth, M. (1999). Countdown to first certificate. Oxford: Oxford University Press.
Trích dẫn kiểu ChicagoDuckworth, Michael. Countdown to First Certificate. Oxford: Oxford University Press, 1999.
MLA引文Duckworth, Michael. Countdown to First Certificate. Oxford: Oxford University Press, 1999.
警告：这些引文格式不一定是100％准确.