@article{DE_1968_4_7_a6,
     author = {V. D. Nguy\^en},
     title = {Vibrations of nonautonomous systems with resonance, in the singular case},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1233--1240},
     publisher = {mathdoc},
     volume = {4},
     number = {7},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_7_a6/}
}