A vowel is here said to have basic length if it is long in all the alternants of the unit : e.g. the second /Ə/ in 'p∂l∂·la'. - Harris (1942a), a pag.173
[A vowel is here said to have basic length] if it is always short while each of its neighboring vowels is either always long or always short. - Harris (1942a), a pag.173, n.11