@article{DE_1970_6_3_a11,
     author = {G. M. Kesel'man and V. \`E. Lyantse},
     title = {The expansion in principal functions of a nonselfadjoint differential operator of order $2n$ with spectral singularities},
     journal = {Differencialʹnye uravneni\^a},
     pages = {497--512},
     publisher = {mathdoc},
     volume = {6},
     number = {3},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1970_6_3_a11/}
}