@article{DE_1986_22_5_a29,
     author = {N. P. Morozov},
     title = {Periodic solutions of the equation $\ddot x+\lambda f(ax+b\dot x)\dot x+x=0$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {905--907},
     publisher = {mathdoc},
     volume = {22},
     number = {5},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1986_22_5_a29/}
}