Found:

Tone stability

PHONOLOGY: a phenomenon found in tone languages. A segment can be deleted while leaving behind the specification of tone height. This specification is found on a neighboring segment, often creating a contour tone. In Margi the two morphemes /ng?/ and /y?/ are realized as [ngya]. The vowel [e] is deleted, leaving behind the low tone. This low tone settles on the remaining vowel and forms a contour tone with the original tone of the second vowel.

LIT.	Goldsmith (1976)