Sz. Shi et Bw. Wang, GEOMETRIC CONDITIONS OF DIFFERENTIABILITY FOR A REGULAR LOCALLY LIPSCHITZ FUNCTION, Acta Mathematica Sinica, New Series, 14(2), 1998, pp. 209-222
The differentiability of a norm of a Banach space may be characterized
by its unit sphere. This paper generalizes these geometric conditions
of norm's differentiability to the case of a. regular locally Lipschi
tz function.