@Article{ ButOudVel15, author = { Buttazzo, Giuseppe and Oudet, Edouard and Velichkov, Bozhidar }, title = { A free boundary problem arising in PDE optimization }, journal = { Calc. Var. PDE }, year = { 2015 }, pages = { }, URL = { http://cvgmt.sns.it/paper/2707/ }, note = { cvgmt preprint} }