@article{IVM_1969_6_a8,
     author = {N. A. Ivaniv},
     title = {The differentiability of functions},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {67--70},
     publisher = {mathdoc},
     number = {6},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1969_6_a8/}
}