Coffin, B. (1980). Coffin's overtones of bel canto: Phonetic basis of artistic singing with 100 chromatic vowel-chart exercises / by Berton Coffin. Scarecrow Press.
Lua i Stíl Chicago (17ú heag.)Coffin, Berton. Coffin's Overtones of Bel Canto: Phonetic Basis of Artistic Singing with 100 Chromatic Vowel-chart Exercises / by Berton Coffin. Metuchen, N.J.: Scarecrow Press, 1980.
Lua MLA (8ú heag.)Coffin, Berton. Coffin's Overtones of Bel Canto: Phonetic Basis of Artistic Singing with 100 Chromatic Vowel-chart Exercises / by Berton Coffin. Scarecrow Press, 1980.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.