1. Fairbanks, Grant. 1960.Voice and Articulation Drillbook, 2nd, 170New York: Harper and Row.
2. Thurman, Wayne L. 1953. “The Construction and Acoustic Analyses of Recorded Scales of Severity for Six Voice Quality Disorders,”. 5Purdue unpubl. diss.
3. The Influence Of Certain Vowel Types On Degree Of Harsh Voice Quality
4. Recent Experimental Investigations of Vocal Pitch in Speech