@article{FAA_1968_2_2_a5,
     author = {B. M. Levitan and G. A. Suvorchenkova},
     title = {Sufficient conditions for a discrete spectrum in the case of a {Sturm--Liouville} equation with operator coefficients},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {56--62},
     publisher = {mathdoc},
     volume = {2},
     number = {2},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1968_2_2_a5/}
}