1. Bettinghaus, Edwin P. 1968.Persuasive Communication, 152–157. New York: Holt, Rinehart & Winston.
2. Blankenship, Jane. 1966.Public Speaking, 9–92. Englewood Cliffs, N. J.: Prentice‐Hall.
3. Cronkhite, Gary. 1969.Persuasion: Speech and Behavioral Change, 195–204. New York: Bobbs‐Merrill.
4. McCroskey, James C. 1968.An Introduction to Rhetorical Communication, 150–151. Englewood Cliffs, N. J.: BobbsMerrill.