@article{MZM_2007_81_6_a7,
     author = {S. Ya. Novikov},
     title = {Bessel {Sequences} as {Projections} of {Orthogonal} {Systems}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {893--903},
     publisher = {mathdoc},
     volume = {81},
     number = {6},
     year = {2007},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2007_81_6_a7/}
}