Whitney, N. (1994). Open doors: Student's book 1. Oxford: Oxford University Press.
Trích dẫn kiểu ChicagoWhitney, Norman. Open Doors: Student's Book 1. Oxford: Oxford University Press, 1994.
Deismireacht MLAWhitney, Norman. Open Doors: Student's Book 1. Oxford: Oxford University Press, 1994.
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