@article{MZM_2002_71_2_a13,
     author = {N. F. Valeev},
     title = {On the {Density} of {Discrete} {Spectra} of {Sturm--Liouville} {Singular} {Operators}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {307--311},
     publisher = {mathdoc},
     volume = {71},
     number = {2},
     year = {2002},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2002_71_2_a13/}
}