@article{DE_1973_9_8_a7,
     author = {L. A. Cherkas},
     title = {The cycles of the equation $y'=Q_2(x,y)/P_2(x,y)$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1432--1437},
     publisher = {mathdoc},
     volume = {9},
     number = {8},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_8_a7/}
}