@article{SM_1968_4_3_a0,
     author = {Yu. G. Reshetnyak},
     title = {Generalized derivatives and differentiability almost everywhere},
     journal = {Sbornik. Mathematics},
     pages = {293--302},
     publisher = {mathdoc},
     volume = {4},
     number = {3},
     year = {1968},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1968_4_3_a0/}
}