@article{MZM_1975_17_4_a14,
     author = {V. I. Filippenko},
     title = {Multiplicity of the spectrum of a~self-adjoint ordinary differential operator of odd order},
     journal = {Matemati\v{c}eskie zametki},
     pages = {631--638},
     publisher = {mathdoc},
     volume = {17},
     number = {4},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1975_17_4_a14/}
}