@article{MZM_1972_12_5_a4,
     author = {V. N. Gabushin},
     title = {The best approximation of the differentiation operator in the metric of~$L_p$},
     journal = {Matemati\v{c}eskie zametki},
     pages = {531--538},
     publisher = {mathdoc},
     volume = {12},
     number = {5},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1972_12_5_a4/}
}