@article{DE_1967_3_10_a5,
     author = {G. I. Shilova},
     title = {The number of periodic solutions of the second kind to the differential equation $\ddot{\varphi}-f_1(\varphi)\dot{\varphi}-f_0(\varphi)=0$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1682--1691},
     publisher = {mathdoc},
     volume = {3},
     number = {10},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1967_3_10_a5/}
}