Ruth Gairns. (2003). Natural english (upper- intermediate student's book). Oxford, NY: Oxford Univ. Press.
Trích dẫn kiểu ChicagoRuth Gairns. Natural English (upper- Intermediate Student's Book). Oxford, NY: Oxford Univ. Press, 2003.
Deismireacht MLARuth Gairns. Natural English (upper- Intermediate Student's Book). Oxford, NY: Oxford Univ. Press, 2003.
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