HEDINGER, Robert, Akoose, su silcam.org, 2011. URL consultato il 17 marzo 2013.
«Among the short vowels the two a-sounds and the two o-sounds are in complementary distribution and therefore do not have to be distinguished in the orthography. However, there is a problem in the long vowels where the two pairs of sounds distinguish between distinct words. Up to now they have not been distinguished and it seems this doesn’t cause any problem to readers.»
