Esling (2010), p. 695. Esling, John H. (2010), "Phonetic Notation", in Hardcastle, William J.; Laver, John; Gibbon, Fiona E. (eds.), The Handbook of Phonetic Sciences (2nd ed.), Wiley-Blackwell, pp. 678–702, doi:10.1002/9781444317251.ch18, ISBN978-1-4051-4590-9
Esling (2010), p. 688. Esling, John H. (2010), "Phonetic Notation", in Hardcastle, William J.; Laver, John; Gibbon, Fiona E. (eds.), The Handbook of Phonetic Sciences (2nd ed.), Wiley-Blackwell, pp. 678–702, doi:10.1002/9781444317251.ch18, ISBN978-1-4051-4590-9