Butterfield, J. (2010). Verbal communication: Illustrated course guides (Second edition.). Course Technology, Cengage Learning.
Chicago-viite (17. p.)Butterfield, Jeff. Verbal Communication: Illustrated Course Guides. Second edition. Australia: Course Technology, Cengage Learning, 2010.
MLA-viite (9. p.)Butterfield, Jeff. Verbal Communication: Illustrated Course Guides. Second edition. Course Technology, Cengage Learning, 2010.
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