@article{TM_1987_180_a62,
     author = {P. V. Zaderej},
     title = {Approximation of differentiable periodic functions of two variables by {Fourier} sums},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {114--115},
     publisher = {mathdoc},
     volume = {180},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1987_180_a62/}
}