@article{DE_1971_7_11_a3,
     author = {E. D. Zhitelzeif},
     title = {The limit cycles of a certain autonomous system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1967--1973},
     publisher = {mathdoc},
     volume = {7},
     number = {11},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_11_a3/}
}