@article{DAN_1960_132_1_a9,
     author = {L. V. Ovsyannikov},
     title = {Determination of the group of a linear second-order differential equation},
     journal = {Doklady Akademii Nauk},
     pages = {44--47},
     year = {1960},
     volume = {132},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_132_1_a9/}
}