@article{FAA_2009_43_4_a7,
     author = {A. Portaluri},
     title = {Indefinite {Sturm} {Theory}},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {91--96},
     publisher = {mathdoc},
     volume = {43},
     number = {4},
     year = {2009},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_2009_43_4_a7/}
}