@article{MZM_1982_31_6_a5,
     author = {E. A. Sevast'yanov},
     title = {Mean modulus of oscillation and piecewise monotone approximation},
     journal = {Matemati\v{c}eskie zametki},
     pages = {867--876},
     publisher = {mathdoc},
     volume = {31},
     number = {6},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1982_31_6_a5/}
}