@article{IVM_2015_11_a0,
     author = {S. B. Vakarchuk and A. V. Shvachko},
     title = {Inequalities of {Kolmogorov's} type for derived functions in two variables and application to approximation by an ``angle''},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {3--22},
     publisher = {mathdoc},
     number = {11},
     year = {2015},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_2015_11_a0/}
}