Etymograph > Indo-European > Old Norse > Rules > on-vowel-deletion

Source: Faarlund 2010:13

i > if previous sound is stressed long front vowel
a > if previous sound is stressed long back open vowel
the book says 'back, labial vowel' but this doesn't match example I think?
u > if previous sound is stressed long back vowel

Referencing rules

on-morpheme-assimilation