@article{MZ_1936__41_168673,
     author = {A. S. Besicovitch},
     title = {On differentiation of functions of two variables},
     journal = {Mathematische Zeitschrift},
     pages = {402--404},
     publisher = {mathdoc},
     volume = {41},
     year = {1936},
     zbl = {0014.10602},
     url = {http://geodesic.mathdoc.fr/item/MZ_1936__41_168673/}
}