@article{DE_1973_9_8_a1,
     author = {\`E. F. Gasinskaya and K. S. Sibirskii},
     title = {Affine invariants of a system with quadratic nonlinearities},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1371--1382},
     publisher = {mathdoc},
     volume = {9},
     number = {8},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_8_a1/}
}