↑Kodzasov, S. V. Pharyngeal Features in the Daghestan Languages. Proceedings of the Eleventh International Congress of Phonetic Sciences (Tallinn, Estonia, Aug 1-7 1987), pp. 142-144.
↑Zeki Hassan, John Esling, Scott Moisik, & lise Crevier-Buchman (2011) "Aryepiglottic trilled variants of /ʕ, ħ/ in Iraqi Arabic". Proceedings of the 17th International Congress of Phonetic Sciences (pp. 831–834), Hong Kong.
↑Mr. Christfried Naumann, Doctoral Student, Department of Linguistics, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. June 26, 2009.
Ladefoged, Peter; Maddieson, Ian, The Sounds of the World's Languages, Oxford: Blackwell, 1996, ISBN 0-631-19815-6