Sprigg Richard Keith. Lepcha and Balti Tibetan: tonal or non-tonal languages?

Asia Major (New Series), 1966 №12, pp. 185-201.Classifying Lepcha as a stress language will result in dividing Lepcha from Balti Tibetan and other tone languages. The two distinctive pitch levels of Lepcha, restricted though their function is, will earn Lepcha a special status among stress languages.Tone-language criteria.
Degree to which lexically distinctive pitch is used.
Pitch and breath force: tone and stress.