 Some modern studies show that Armenian is as close to Indo-Iranian as it is to Greek and Phrygian.An alternate theory suggests that speakers of Proto-Armenian were tribes indigenous to the northern Armenian highlands, such as the Hayasans, Diauehi, and/or Etiuni.Although these groups are only known only from references left by neighboring peoples (such as Hittites, Urartians, and Assyrians), Armenian etymologies have been proposed for their names.