1. [BS] Yu. E. Borovskii and S. Z. Shefel',One Chern-Kuiper Theorem, Siberian Math. J.,19 (6): (1979), 978?979.
2. [BZ] Yu. Burago, V. Zalgaller,Geometric Inequalities, Springer-Verlag, New York, (1988).
3. [C1] M. P. do Carmo,Differentiable Curves and Surfaces, Prentice-Hall, New Jersey, (1976).
4. [C2] M. P. do Carmo,Geometria Riemanniana, IMPA, Rio de Janeiro, (1988).
5. [CE] J. Cheeger and D. Ebin,Comparison Theorems in Riemannian Geometry, North-Holland Publishing Co., New York, (1975).