@article{DAN_1969_189_4_a3,
     author = {V. A. Il'in and I. A. Shishmarev},
     title = {Fourier series in fundamental systems of functions of the polyharmonic operator},
     journal = {Doklady Akademii Nauk},
     pages = {707--709},
     publisher = {mathdoc},
     volume = {189},
     number = {4},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_189_4_a3/}
}