1. Lewis, George L., Everett, Russel, Gibson, James W. and Schoen, Kathryn T. 1969.Teaching Speech, 141–145. Columbus, Ohio: Charles E. Merrill Pub. Co.
2. Robinson, Karl F. and Becker, Albert B. 1970.Effective Speech for the Teacher, 103–104. New York: McGraw Hill Book Co.
3. Fessenden, Seth A. 1968.Speech for the Creative Teacher, 254–256. Dubuque: Wm. C. Brown.