@article{JEMS_2015_17_4_a3,
     author = {Pierre Bousquet and Augusto C. Ponce and Jean Van Schaftingen},
     title = {Strong density for higher order {Sobolev} spaces into compact manifolds},
     journal = {Journal of the European Mathematical Society},
     pages = {763--817},
     publisher = {mathdoc},
     volume = {17},
     number = {4},
     year = {2015},
     doi = {10.4171/jems/518},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/jems/518/}
}