@article{JEMS_2018_20_3_a1,
     author = {Stanislav Hencl and Aldo Pratelli},
     title = {Diffeomorphic approximation of $W^{1,1}$ planar {Sobolev} homeomorphisms},
     journal = {Journal of the European Mathematical Society},
     pages = {597--656},
     publisher = {mathdoc},
     volume = {20},
     number = {3},
     year = {2018},
     doi = {10.4171/jems/774},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/jems/774/}
}