@Article{ gbuest01, author = { Buttazzo, Giuseppe and Stepanov, Eugene }, title = { Transport density in Monge-Kantorovich problems with Dirichlet conditions }, journal = { Discrete Contin. Dyn. Syst. }, year = { 2005 }, volume = { 12 }, number = { 4 }, pages = { 607-628 }, URL = { http://cvgmt.sns.it/paper/237/ }, note = { cvgmt preprint} }