Guffey, M. E. (1995). Essentials of business communication (3rd ed.). South-Western College.
Lua i Stíl Chicago (17ú heag.)Guffey, Mary Ellen. Essentials of Business Communication. 3rd ed. Cincinnati, Ohio: South-Western College, 1995.
Lua MLA (9ú heag.)Guffey, Mary Ellen. Essentials of Business Communication. 3rd ed. South-Western College, 1995.
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