@article{DAN_1963_153_6_a7,
     author = {A. Yu. Levin},
     title = {On linear second-order differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {1257--1260},
     publisher = {mathdoc},
     volume = {153},
     number = {6},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_153_6_a7/}
}