@article{MZM_1999_66_6_a9,
     author = {A. M. Savchuk and A. A. Shkalikov},
     title = {Sturm--Liouville operators with singular potentials},
     journal = {Matemati\v{c}eskie zametki},
     pages = {897--912},
     publisher = {mathdoc},
     volume = {66},
     number = {6},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1999_66_6_a9/}
}