@Article{ belnovorl11, author = { Bellettini, Giovanni and Novaga, Matteo and Orlandi, Giandomenico }, title = { Lorentzian varifolds and applications to closed relativistic strings }, journal = { Indiana Univ. Math. J. }, year = { 2012 }, volume = { 61 }, number = { 6 }, pages = { 2251-2310 }, URL = { http://cvgmt.sns.it/paper/1563/ }, note = { cvgmt preprint} }