@article{DE_1973_9_8_a15,
     author = {N. N. Butenina},
     title = {Bifurcations of the separatrices and limit cycles of a two-dimensional dynamical system under a rotation of the field},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1520--1522},
     publisher = {mathdoc},
     volume = {9},
     number = {8},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_8_a15/}
}