Found:

Ablaut

MORPHOLOGY: a process by which an inflected form of a word is formed by changing the vowel of the base. EXAMPLE: in English it is possible to derive the past tense of strong verbs by substituting the base vowel by another vowel: get:got, sing:sang and fall:fell.

LIT.	Bloomfield (1933) Halle, M. & K.P. Mohanan (1985) Scalise, S. (1984) Spencer, A. (1991)