@article{DAN_1961_139_3_a1,
     author = {K. K. Golovkin},
     title = {Certain conditions for the smoothness of a function of several variables and estimates of convolution operators},
     journal = {Doklady Akademii Nauk},
     pages = {524--527},
     publisher = {mathdoc},
     volume = {139},
     number = {3},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_139_3_a1/}
}