@article{DE_1988_24_10_a24,
     author = {N. P. Morozov},
     title = {Periodic solutions of the equation $\ddot x+\lambda f(x,\dot x)\dot x+x=0$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1826--1828},
     publisher = {mathdoc},
     volume = {24},
     number = {10},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_10_a24/}
}