Global Properties of Immersions into Euclidean Spheres James White Indiana University Mathematics Journal 1971 text pdf 10.1512/iumj.1971.20.20109 10.1512/iumj.1971.20.20109 en Indiana Univ. Math. J. 20 (1971) 1187 - 1194 state-of-the-art mathematics http://iumj.org/access/