@article{DE_1966_2_7_a4,
     author = {K. S. Sibirskii},
     title = {Invariants of linear representations of the rotation group of the plane and their applications in the qualitative theory of differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {908--918},
     publisher = {mathdoc},
     volume = {2},
     number = {7},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_7_a4/}
}