@article{DAN_1991_319_4_a5,
     author = {V. P. Gromov},
     title = {Nontrivial expansion of zero and representative systems of the},
     journal = {Doklady Akademii Nauk},
     pages = {801--805},
     publisher = {mathdoc},
     volume = {319},
     number = {4},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_319_4_a5/}
}