@article{DE_1968_4_10_a3,
     author = {I. A. Pavlyuk},
     title = {The investigation of nonautonomous systems of second order differential equations by means of differential invariants},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1785--1800},
     publisher = {mathdoc},
     volume = {4},
     number = {10},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_10_a3/}
}