Maddieson, Ian. 2008. Absence of Common 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 18. Available online at http://wals.info/feature/18Archived 2009-06-01 at the Wayback Machine. Accessed on 2008-09-15.
Maddieson, Ian. 2008. Absence of Common 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 18. Available online at http://wals.info/feature/18Archived 2009-06-01 at the Wayback Machine. Accessed on 2008-09-15.