Singularities of Quasiconformal Deformations in R^n J. Sarvas Indiana University Mathematics Journal 1982 text pdf 10.1512/iumj.1982.31.31013 10.1512/iumj.1982.31.31013 en Indiana Univ. Math. J. 31 (1982) 121 - 134 state-of-the-art mathematics http://iumj.org/access/