@article{DE_1980_16_3_a5,
     author = {G. S. Rychkov},
     title = {Uniqueness of the limit cycle of the equation $(y-P_3(x))dy=P_1(x,y)dx$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {433--437},
     publisher = {mathdoc},
     volume = {16},
     number = {3},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1980_16_3_a5/}
}