Gude, K., & Duckworth, M. (1994). Proficiency masterclass: Student's book. Oxford: Oxford University Press.
Trích dẫn kiểu ChicagoGude, Kathy., và Michael Duckworth. Proficiency Masterclass: Student's Book. Oxford: Oxford University Press, 1994.
Deismireacht MLAGude, Kathy., và Michael Duckworth. Proficiency Masterclass: Student's Book. Oxford: Oxford University Press, 1994.
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