@article{DE_1987_23_2_a10,
     author = {L. A. Cherkas and I. S. Shchukina},
     title = {On series expansion of an {Andronov--Hopf} manifold of a quadratic system in the plane},
     journal = {Differencialʹnye uravneni\^a},
     pages = {278--282},
     publisher = {mathdoc},
     volume = {23},
     number = {2},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1987_23_2_a10/}
}