Modifications and Cobounding Manifolds, IV Andrew Wallace Indiana University Mathematics Journal 1963 text pdf 10.1512/iumj.1963.12.12029 10.1512/iumj.1963.12.12029 en Indiana Univ. Math. J. 12 (1963) 445 - 484 state-of-the-art mathematics http://iumj.org/access/