@Article{ butsan03, author = { Buttazzo, Giuseppe and Santambrogio, Filippo }, title = { A Model for the Optimal Planning of an Urban Area }, journal = { SIAM J. Math. Anal. }, year = { 2005 }, volume = { 37 }, number = { 2 }, pages = { 514-530 }, URL = { http://cvgmt.sns.it/paper/1167/ }, note = { cvgmt preprint} }