W. H. George, The Sounds of Music: The Trumpet, Hi—fi News, August 1965, pp.214-216
Gertsman 1988: E.V. Gertsman, Instrumental catalogue by Pollux, In the book: From the History of Instrumental Musical Culture, Leningrad, p. 22, Ref to circular breathing on the aulos/tibia
Gevaert 1875: Histoire et theorie de la musique de l’antiquite
Personal filing reference: N/A