References
- Semi-Riemannain geometry with application to relativity B. O'Neil
- Geometry of submanifold B. Y. Chen
- Proc. Japan Acad. v.71 Warped products with critical Riemannian metric B. H. Kim
- Trans. Amer. Math. Soc. v.145 Manifolds of negative curvature R. L. Bishop;B. O'Neil
- Soochow J. Math. v.5 Totally umbilical submanifolds B. Y. Chen
- Einstein manifolds A. Besse