Spherical Compact Hypersurfaces Robert Hermann Indiana University Mathematics Journal 1964 text pdf 10.1512/iumj.1964.13.13014 10.1512/iumj.1964.13.13014 en Indiana Univ. Math. J. 13 (1964) 237 - 242 state-of-the-art mathematics http://iumj.org/access/