Guffey, M. E. (1999). Business English (6th ed.). Cincinnati, Ohio: South-Western College.
Trích dẫn kiểu ChicagoGuffey, Mary Ellen. Business English. 6th ed. Cincinnati, Ohio: South-Western College, 1999.
Deismireacht MLAGuffey, Mary Ellen. Business English. 6th ed. Cincinnati, Ohio: South-Western College, 1999.
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