@article{IM2_1994_43_2_a3,
     author = {M. G. Grigoryan},
     title = {On~some properties of orthogonal systems},
     journal = {Izvestiya. Mathematics},
     pages = {261--289},
     year = {1994},
     volume = {43},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1994_43_2_a3/}
}