@article{RM_2008_63_1_a2,
     author = {Yu. V. Pokornyi and M. B. Zvereva and S. A. Shabrov},
     title = {Sturm{\textendash}Liouville oscillation theory for impulsive problems},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {109--153},
     year = {2008},
     volume = {63},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_2008_63_1_a2/}
}