Analysis vs. Geometry on a Class of Rectifiable Hypersurfaces in R^n Stephen Semmes Indiana University Mathematics Journal 1990 text pdf 10.1512/iumj.1990.39.39048 10.1512/iumj.1990.39.39048 en Indiana Univ. Math. J. 39 (1990) 1005 - 1035 state-of-the-art mathematics http://iumj.org/access/