@article{MZM_1984_36_6_a9,
     author = {N. N. Sorich and A. I. Stepanets},
     title = {Simultaneous approximation of periodic functions and their derivatives},
     journal = {Matemati\v{c}eskie zametki},
     pages = {873--882},
     publisher = {mathdoc},
     volume = {36},
     number = {6},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1984_36_6_a9/}
}