@article{DE_1970_6_7_a0,
     author = {V. A. Il'in},
     title = {A generalized principle of localization for the {Riesz} means of a {Fourier} series in an arbitrary fundamental system of functions of the {Laplace} operator with discrete spectrum},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1143--1158},
     publisher = {mathdoc},
     volume = {6},
     number = {7},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1970_6_7_a0/}
}