@article{IVM_1967_9_a3,
     author = {L. B. Zelenko},
     title = {Conditions for the semiboundedness and discreteness of the spectrum of the {Sturm{\textendash}Liouville} operator on the semi-axis},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {31--40},
     year = {1967},
     number = {9},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1967_9_a3/}
}