@article{MZM_1984_36_5_a2,
     author = {M.-B. Babayev},
     title = {Extremal properties and two-sided estimates in approximation by sums of functions of lesser number of variables},
     journal = {Matemati\v{c}eskie zametki},
     pages = {647--659},
     publisher = {mathdoc},
     volume = {36},
     number = {5},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1984_36_5_a2/}
}