@article{MZM_1987_42_6_a5,
     author = {A. B. Budak and V. N. Denisov},
     title = {Some properties of characteristic functions of the {Sturm--Liouville} operator with discontinuous coefficients},
     journal = {Matemati\v{c}eskie zametki},
     pages = {819--830},
     publisher = {mathdoc},
     volume = {42},
     number = {6},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1987_42_6_a5/}
}