@article{DE_1992_28_3_a19,
     author = {Z. S. Batalova and N. V. Buhalova},
     title = {Investigation of periodic solutions of a differential equation of pendulum type},
     journal = {Differencialʹnye uravneni\^a},
     pages = {516--519},
     publisher = {mathdoc},
     volume = {28},
     number = {3},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1992_28_3_a19/}
}