L. Caravenna and S. Daneri, The disintegration of the Lebesgue measure on the faces of a convex function, J. Funct. Anal. 258 (2010), 3604-3661.
S. Daneri and A. Pratelli, Smooth approximation of bi-Lipschitz orientation- preserving homeomorphisms, preprint (2011). [http://arxiv.org/abs/1106.1192]