@article{DE_1985_21_12_a7,
     author = {A. E. Rudenok},
     title = {Limit cycles of a two-dimensional autonomous system with quadratic nonlinearities},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2072--2082},
     publisher = {mathdoc},
     volume = {21},
     number = {12},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_12_a7/}
}