@article{DE_1966_2_6_a9,
     author = {V. A. Il'in},
     title = {Riesz means, {Ces\`aro} and {Poisson--Abel} summability of {Fourier} series of eigenfunctions},
     journal = {Differencialʹnye uravneni\^a},
     pages = {816--827},
     publisher = {mathdoc},
     volume = {2},
     number = {6},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_6_a9/}
}