@article{MZM_1973_14_3_a5,
     author = {M. Otelbaev and Ya. T. Sultanaev},
     title = {On the formula for the distribution of the eigenvalues of singular differential operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {361--368},
     publisher = {mathdoc},
     volume = {14},
     number = {3},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1973_14_3_a5/}
}