@article{DAN_1971_196_6_a7,
     author = {V. N. Sudakov},
     title = {On a problem of {Birkhoff}},
     journal = {Doklady Akademii Nauk},
     pages = {1280--1282},
     publisher = {mathdoc},
     volume = {196},
     number = {6},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_196_6_a7/}
}