@article{DE_1978_14_5_a3,
     author = {G. M. Buldyk},
     title = {The existence of limit cycles of the equation $(1+x)yy'=-P_4(x)-P_2(x)y+\delta y^2$ in a singular case},
     journal = {Differencialʹnye uravneni\^a},
     pages = {817--823},
     publisher = {mathdoc},
     volume = {14},
     number = {5},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1978_14_5_a3/}
}