@article{DE_2003_39_5_a4,
     author = {B. T. Bilalov},
     title = {Bases of {Exponentials,} {Cosines,} and {Sines} {Formed} by {Eigenfunctions} of {Differential} {Operators}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {619--623},
     publisher = {mathdoc},
     volume = {39},
     number = {5},
     year = {2003},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2003_39_5_a4/}
}