> It's also unclear whether zero or °
> is always from *a or from any other vowel.
Arnaud
============
Not. Zero degree of the two other vowels are *i and *u, not zero.
Torsten
=======
What is the vowel in pt-eron ?
from root *p_t (or *pet if you prefer)
I see zero vowel.
What do you see ?
Arnaud
===========