Semihandles and 4-Manifolds Dallas Webster Indiana University Mathematics Journal 1974 text pdf 10.1512/iumj.1974.23.23095 10.1512/iumj.1974.23.23095 en Indiana Univ. Math. J. 23 (1974) 1199 - 1202 state-of-the-art mathematics http://iumj.org/access/