@article{DAN_1970_191_1_a3,
     author = {V. A. Il'in},
     title = {Exact conditions for the localization and convergence of {Fourier} series in fundamental function systems of the {Beltrami} operator},
     journal = {Doklady Akademii Nauk},
     pages = {20--21},
     publisher = {mathdoc},
     volume = {191},
     number = {1},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1970_191_1_a3/}
}