1. S. Sternberg,Lectures on Differential Geometry, Prentice-Hall, Englewood Cliffs, N.J., (1970).
2. S. S. Chern and R. K. Lashof, “The total curvature of immersed manifolds,”Amer. J. Math.,79, 308–318 (1957).
3. S. Heijenoort, “On locally convex manifolds,”Communications on Pure and Applied Mathematics,5, 223–242 (1952).
4. C. Currier, “On hypersurfaces of Hyperbolic space infinitesimally supported by horospheres,”Trans. Amer. Math. Soc.,313, No. 1, 420–431 (1989).
5. A. A. Borisenko and D. I. Vlasenko, “Convex surfaces in the Lobachevskii space,”Mat. Fiz. Anal. Geom.,4, No. 3, 278–285 (1997).