@article{IM2_2001_65_5_a5,
     author = {S. N. Tumanov},
     title = {Asymptotic formulae for the real eigenvalues of the {Sturm--Liouville} problem with two turning points},
     journal = {Izvestiya. Mathematics },
     pages = {1003--1016},
     publisher = {mathdoc},
     volume = {65},
     number = {5},
     year = {2001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2001_65_5_a5/}
}