Barrall, I., & Barrall, N. (2009). Intelligent Business Elementary Coursebook & Workbook. Hà Nội: Từ điển Bách khoa.
Παραπομπή Chicago StyleBarrall, Irene, και Nikolas Barrall. Intelligent Business Elementary Coursebook & Workbook. Hà Nội: Từ điển Bách khoa, 2009.
Παραπομπή MLABarrall, Irene, και Nikolas Barrall. Intelligent Business Elementary Coursebook & Workbook. Hà Nội: Từ điển Bách khoa, 2009.
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