@article{JRAM_1995__458_153677,
     author = {Olli Martio and Jan Maly},
     title = {Lusin's condition {(N)} and mappings of the class {W1,} n.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {19--36},
     publisher = {mathdoc},
     volume = {458},
     year = {1995},
     zbl = {0812.30007},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1995__458_153677/}
}