@article{MZM_2003_74_1_a15,
     author = {V. G. Krotov},
     title = {When is an {Orthogonal} {Series} a {Fourier} {Series?}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {139--142},
     publisher = {mathdoc},
     volume = {74},
     number = {1},
     year = {2003},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2003_74_1_a15/}
}