H. Alencar et M. Docarmo, HYPERSURFACES WITH CONSTANT MEAN-CURVATURE IN SPHERES, Proceedings of the American Mathematical Society, 120(4), 1994, pp. 1223-1229
Let M(n) be a compact hypersurface of a sphere with constant mean curv
ature H. We introduce a tensor phi, related to H and to the second fun
damental form, and show that if \phi\2 < B(H), where B(H) not-equal 0
is a number depending only on H and n, then either 10(12) = 0 or \phi\
2 = B(H). We also characterize all M(n) with \phi\2 = B(H).