@article{FPM_1999_5_2_a12,
     author = {M. K. Potapov and F. M. Berisha},
     title = {On the connection between a~$r$-order modulus of smoothness and the~best approximation by algebraic polynomials},
     journal = {Fundamentalʹna\^a i prikladna\^a matematika},
     pages = {563--587},
     publisher = {mathdoc},
     volume = {5},
     number = {2},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FPM_1999_5_2_a12/}
}