Ian Maddieson (2008) "Glottalic Consonants". In: Martin Haspelmath & Matthew S. Dryer & David Gil & Bernard Comrie (eds.) The World Atlas of Language Structures Online. Munich: Max Planck Digital Library, chapter 7. Available online at http://wals.info/feature/7. Accessed on 18 January 2011
Ian Maddieson (2008) "Presence of Uncommon Consonants". In: Martin Haspelmath & Matthew S. Dryer & David Gil & Bernard Comrie (eds.) The World Atlas of Language Structures Online. Munich: Max Planck Digital Library, chapter 19. Available online at http://wals.info/feature/19. Accessed on 18 January 2011
