@article{DAN_1961_140_1_a7,
     author = {R. S. Ismagilov},
     title = {Conditions for the semiboundedness and discreteness of the spectrum in the case of one-dimensional differential operators},
     journal = {Doklady Akademii Nauk},
     pages = {33--36},
     publisher = {mathdoc},
     volume = {140},
     number = {1},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_140_1_a7/}
}