@article{RM_1973_28_4_a15,
     author = {I. E. Gopengauz},
     title = {Difference properties and differentiability of functions of several variables},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {28},
     number = {4},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1973_28_4_a15/}
}