Cita APA (7th ed.)

Butterfield, J. (2010). Verbal communication. Course Technology, Cengage Learning.

Cita Chicago (17th ed.)

Butterfield, Jeff. Verbal Communication. Australia: Course Technology, Cengage Learning, 2010.

Cita MLA (9th ed.)

Butterfield, Jeff. Verbal Communication. Course Technology, Cengage Learning, 2010.