@article{DAN_1993_333_2_a0,
     author = {V. A. Il'in and E. I. Moiseev},
     title = {Some nonclassical singularities of a spectral problem for an},
     journal = {Doklady Akademii Nauk},
     pages = {133--135},
     publisher = {mathdoc},
     volume = {333},
     number = {2},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1993_333_2_a0/}
}