The Dferential Geometry of Foliations, II Robert Hermann Indiana University Mathematics Journal 1962 text pdf 10.1512/iumj.1962.11.11019 10.1512/iumj.1962.11.11019 en Indiana Univ. Math. J. 11 (1962) 303 - 315 state-of-the-art mathematics http://iumj.org/access/