@article{DE_1985_21_6_a9,
     author = {G. S. Rychkov},
     title = {The maximum number of limit cycles of the equation $(y-P_3(x))dy=P_1(x,y)dx$ in the case of three singular points},
     journal = {Differencialʹnye uravneni\^a},
     pages = {991--997},
     publisher = {mathdoc},
     volume = {21},
     number = {6},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_6_a9/}
}