@article{DE_1972_8_11_a8,
     author = {D. K. Lika and Yu. A. Ryabov},
     title = {Convergence of the small parameter method in the construction of periodic solutions of ordinary differential equations of neutral type with small lag},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1977--1987},
     publisher = {mathdoc},
     volume = {8},
     number = {11},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_11_a8/}
}