@article{ZAA_2000__19_3_48971,
     author = {Farkas, G. and Garay, B.M.},
     title = {A non-differentiablity result for the inversion operator between {Sobolev} spaces.},
     journal = {Zeitschrift f\"ur Analysis und ihre Anwendungen},
     pages = {639--654},
     publisher = {mathdoc},
     volume = {19},
     number = {3},
     year = {2000},
     zbl = {0973.47045},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ZAA_2000__19_3_48971/}
}