@Misc{ BucButNit16, author = { Bucur, Dorin and Buttazzo, Giuseppe and Nitsch, Carlo }, title = { Symmetry breaking for a problem in optimal insulation }, journal = { Journal de Mathématiques Pures et Appliquées }, year = { 2017 }, pages = { }, URL = { http://cvgmt.sns.it/paper/2894/ }, note = { cvgmt preprint} }