@article{10_4007_annals_2010_171_673,
     author = {Luis Caffarelli and Robert J. McCann},
     title = {Free boundaries in optimal transport and {Monge-Amp\`ere} obstacle problems},
     journal = {Annals of mathematics},
     pages = {673--730},
     publisher = {mathdoc},
     volume = {171},
     number = {2},
     year = {2010},
     doi = {10.4007/annals.2010.171.673},
     mrnumber = {2630054},
     zbl = {1196.35231},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4007/annals.2010.171.673/}
}