@article{RM_1986_41_2_a7,
     author = {E. A. Andronova},
     title = {On~the topology of quadratic systems with four (or more) limit cycles},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {191--192},
     publisher = {mathdoc},
     volume = {41},
     number = {2},
     year = {1986},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1986_41_2_a7/}
}