@Article{ CatMasMon14, author = { Catino, Giovanni and Mastrolia, Paolo and Monticelli, Dario Daniele }, title = { A variational characterization of flat spaces in dimension three }, journal = { Pac. J. Math }, year = { 2016 }, volume = { 282 }, number = { 2 }, pages = { 285-292 }, URL = { http://cvgmt.sns.it/paper/2451/ }, note = { cvgmt preprint} }