See Blau (2010:128–129) Long /aː eː oː/ were written as ⟨α η ω⟩, while short /a e o/ were written ⟨α/ε ε ο⟩.
Blau (2010:128–129) Долгие /aː eː oː/ писались как α η ω, тогда как краткие /a e o/ писались α/ε ε ο.