@article{IM2_1972_6_4_a6,
     author = {E. M. Nikishin},
     title = {A~resonance theorem and series in eigenfunctions of the {Laplacian}},
     journal = {Izvestiya. Mathematics },
     pages = {788--806},
     publisher = {mathdoc},
     volume = {6},
     number = {4},
     year = {1972},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1972_6_4_a6/}
}