@article{DAN_1962_145_3_a8,
     author = {I. S. Kats},
     title = {On the spectral multiplicity of a second-order differential operator},
     journal = {Doklady Akademii Nauk},
     pages = {510--513},
     publisher = {mathdoc},
     volume = {145},
     number = {3},
     year = {1962},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1962_145_3_a8/}
}