An Incomplete Compact Homogeneous Lorentz Metric Robert Hermann Indiana University Mathematics Journal 1964 text pdf 10.1512/iumj.1964.13.13029 10.1512/iumj.1964.13.13029 en Indiana Univ. Math. J. 13 (1964) 497 - 501 state-of-the-art mathematics http://iumj.org/access/