1. Breath support directives used by singing teachers: a Delphi study;Spillane;NATS J,1989
2. Some verbal directives regarding support concepts and their effects upon resultant sung tone;Swank;NATS J,1984
3. Singing: the mechanism and the technic;Vennard,1967
4. The science of vocal pedagogy;Appleman,1967
5. The structure of singing: system and art in vocal technique;Miller,1986