@article{VMUMM_1985_6_a16,
     author = {N. A. Bokaev},
     title = {The sum of closed $U$-sets for multiplicative orthonormal systems},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {93--96},
     year = {1985},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1985_6_a16/}
}