Collapsing to Almost Riemannian Spaces Frederick Wilhelm, Jr. Indiana University Mathematics Journal 1992 text pdf 10.1512/iumj.1992.41.41056 10.1512/iumj.1992.41.41056 en Indiana Univ. Math. J. 41 (1992) 1119 - 1142 state-of-the-art mathematics http://iumj.org/access/