@article{DAN_1991_320_3_a5,
     author = {F. G. Maksudov and I. V. Aliev},
     title = {Second-order operator-differential equations with nonregular},
     journal = {Doklady Akademii Nauk},
     pages = {539--542},
     publisher = {mathdoc},
     volume = {320},
     number = {3},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_320_3_a5/}
}