@article{DAN_1980_255_6_a1,
     author = {N. A. Bobylev},
     title = {On a problem of {Ulam}},
     journal = {Doklady Akademii Nauk},
     pages = {1292--1295},
     publisher = {mathdoc},
     volume = {255},
     number = {6},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1980_255_6_a1/}
}