@article{MZM_1992_51_5_a19,
     author = {A. S. Krantsberg},
     title = {On a generalization of the bessel inequality},
     journal = {Matemati\v{c}eskie zametki},
     pages = {149--150},
     publisher = {mathdoc},
     volume = {51},
     number = {5},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1992_51_5_a19/}
}