@article{MZM_2000_67_5_a15,
     author = {N. N. Kholshchevnikova},
     title = {Theorems on unions of $U$-sets},
     journal = {Matemati\v{c}eskie zametki},
     pages = {778--787},
     publisher = {mathdoc},
     volume = {67},
     number = {5},
     year = {2000},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2000_67_5_a15/}
}