@article{DE_1972_8_6_a15,
     author = {E. D. Zhitelzeif},
     title = {The limit cycles of the equation $\ddot x+f(x,\,\dot x)\dot x+g(x)=0$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1095--1097},
     publisher = {mathdoc},
     volume = {8},
     number = {6},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_6_a15/}
}