@article{DE_1975_11_8_a4,
     author = {V. I. Rozhkov},
     title = {A certain method of investigating the periodic solutions of systems with a small parameter multiplying the derivatives},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1388--1395},
     publisher = {mathdoc},
     volume = {11},
     number = {8},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_8_a4/}
}