@article{DE_1973_9_1_a29,
     author = {I. A. Pasynkova},
     title = {Letter to the editors {("The} existence of families of periodic solutions of a system of $n$ second order differential equations in the resonance case{\textquotedblright}, {Differencial'nye} {Uravnenija} 5 (1969), 1984{\textendash}1989)},
     journal = {Differencialʹnye uravneni\^a},
     pages = {192},
     year = {1973},
     volume = {9},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_1_a29/}
}