@article{MZM_1985_38_1_a9,
     author = {S. P. Ponomarev},
     title = {Symmetrically differentiable functions with a perfect set of nondifferentiability points},
     journal = {Matemati\v{c}eskie zametki},
     pages = {80--88},
     publisher = {mathdoc},
     volume = {38},
     number = {1},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1985_38_1_a9/}
}