C. Biasi et O. Saeki, ON THE BETTI NUMBER OF THE IMAGE OF A CODIMENSION-K IMMERSION WITH NORMAL CROSSINGS, Proceedings of the American Mathematical Society, 123(11), 1995, pp. 3549-3554
Let f: M --> N be a codimension- k immersion with normal crossings of
a closed m-dimensional manifold. We show that f is an embedding if and
only if the (m - k + 1)-th Betti numbers of M and f(M) coincide, unde
r a certain condition on the normal bundle of f.