HELGESEN, M. (1995). Workplace English Office File: Student book. Longman.
Lua i Stíl Chicago (17ú heag.)HELGESEN, Marc. Workplace English Office File: Student Book. Longman, 1995.
Lua MLA (8ú heag.)HELGESEN, Marc. Workplace English Office File: Student Book. Longman, 1995.
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