@article{DAN_1982_265_1_a0,
     author = {M.-B. A. Babaev},
     title = {Extremal elements and the value of the best approximation of a monotone function on $R^n$ by sums of functions of fewer variables},
     journal = {Doklady Akademii Nauk},
     pages = {11--13},
     publisher = {mathdoc},
     volume = {265},
     number = {1},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1982_265_1_a0/}
}