@article{DAN_1976_226_5_a6,
     author = {V. V. Tikhomirov},
     title = {On the {Riesz} means of expansions in a trigonometric {Fourier} series and in the eigenfunctions of a {Keldys} pencil of ordinary nonselfadjoint differential operators},
     journal = {Doklady Akademii Nauk},
     pages = {1015--1017},
     publisher = {mathdoc},
     volume = {226},
     number = {5},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1976_226_5_a6/}
}