Maddieson, Ian. 2008. Glottalized Consonants. In: Haspelmath, Martin & Dryer, Matthew S. & Gil, David & Comrie, Bernard (eds.) The World Atlas of Language Structures Online. Munich: Max Planck Digital Library, chapter 7. Available online at http://wals.info/feature/7 Dicapai pada 28 Mac 2008.
