1. J. Hadamard, Sur certaines propriétes des trajectories en dynamique, S. Muth. Pures. Apple, 3 (1897), 331–387.
2. S. S. Chern, R. K. Lashof, The total curvature of immersed manifolds, Amer. S. Math., (1957), 79, 308–318.
3. S. Alexander, Locally convex hypersurfaces of negatively curved spaces, Proc. Amer. Math. Soc., (1977), 64,(2), 321–325.
4. S. Heijenort, On locally convex manofolds, Comm. Pure Appl. Maths, (1952), 5, 223–242.
5. R. Currier, On hypersurfaces of hyperbolic space infinitesimally supported by horospheres, Trans. Amer. Math. Soc., (1989), 313,(1), 412–431.