@article{MZM_1974_16_4_a9,
     author = {V. A. Mikhailets},
     title = {On the nature of the spectrum of self-adjoint extensions of operators admitting separation of variables},
     journal = {Matemati\v{c}eskie zametki},
     pages = {577--584},
     publisher = {mathdoc},
     volume = {16},
     number = {4},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1974_16_4_a9/}
}