@article{IM2_2000_64_4_a1,
     author = {V. A. Vinokurov and V. A. Sadovnichii},
     title = {Asymptotics of any order for the eigenvalues and eigenfunctions of the {Sturm{\textendash}Liouville} boundary-value problem on a~segment with a~summable potential},
     journal = {Izvestiya. Mathematics},
     pages = {695--754},
     year = {2000},
     volume = {64},
     number = {4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2000_64_4_a1/}
}