@article{IM2_1999_63_4_a0,
     author = {P. V. Al'brecht},
     title = {Differentiable operators of nearly best approximation},
     journal = {Izvestiya. Mathematics },
     pages = {631--647},
     publisher = {mathdoc},
     volume = {63},
     number = {4},
     year = {1999},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1999_63_4_a0/}
}