@article{DE_1975_11_4_a1,
     author = {Ya. V. Bykov and K. A. Kiriy},
     title = {Periodic oscillations with large amplitude},
     journal = {Differencialʹnye uravneni\^a},
     pages = {604--610},
     publisher = {mathdoc},
     volume = {11},
     number = {4},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_4_a1/}
}