@article{10_1090_S0894_0347_2013_00763_8,
     author = {Fefferman, Charles and Israel, Arie and Luli, Garving},
     title = {Sobolev extension by linear operators},
     journal = {Journal of the American Mathematical Society},
     pages = {69--145},
     publisher = {mathdoc},
     volume = {27},
     number = {1},
     year = {2014},
     doi = {10.1090/S0894-0347-2013-00763-8},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-2013-00763-8/}
}