@article{VTGU_2011_1_a4,
     author = {M. A. Sadybekov and A. M. Sarsenbi},
     title = {On a~necessary condition for a~system of normalized elements to be a~basis in {a~Hilbert} space},
     journal = {Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mehanika},
     pages = {44--46},
     publisher = {mathdoc},
     number = {1},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VTGU_2011_1_a4/}
}