The Null-Bundle of an Einstein-Riemann Space I: General Theory Dominic Edelen Indiana University Mathematics Journal 1967 text pdf 10.1512/iumj.1967.16.16025 10.1512/iumj.1967.16.16025 en Indiana Univ. Math. J. 16 (1967) 351 - 363 state-of-the-art mathematics http://iumj.org/access/