1. Acoustic impedance of an artificially lengthened and constricted vocal tract;Story;J Voice,2000
2. Freeing the Natural Voice;Linklater,1976
3. Lip trills and raspberries: “High spit factor” alternatives to the nasal continuant consonants;Nix;J Sing,1999
4. Sprecherziehung des Schauspielers: Grundlagen und Methoden;Aderhold,1963
5. Coffin's Sound of Singing. Principles and Applications of Vocal Techniques With Chromatic Vowel Chart;Coffin,1987