@article{DAN_1971_201_5_a6,
     author = {I. I. Ibragimov and M.-B. A. Babayev},
     title = {On estimates of best approximations of a function of several variables by sums of two functions of a smaller number of variables},
     journal = {Doklady Akademii Nauk},
     pages = {1037--1040},
     publisher = {mathdoc},
     volume = {201},
     number = {5},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_201_5_a6/}
}