@article{TM_1971_109_a3,
     author = {Yu. N. Subbotin},
     title = {Approximation by spline functions, and estimates of widths},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {35--60},
     publisher = {mathdoc},
     volume = {109},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1971_109_a3/}
}