1. STINCHFIELD S. M. Speech Disorders. New York: Harcourt Brace & Co. 1933.
2. For a full account of this investigation including the actual tests used the words stammered by each subject and a detailed record of the amount of time each subject was given negative practice the reader is referred to the library of the University of California at Los Angeles where this study in its entirety is present in the form of a Master's Thesis.