@article{MZM_1987_41_5_a3,
     author = {A. V. Kolushov},
     title = {Differential properties of the operator of best approximation of continuous functions by rational fractions},
     journal = {Matemati\v{c}eskie zametki},
     pages = {654--672},
     publisher = {mathdoc},
     volume = {41},
     number = {5},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1987_41_5_a3/}
}