@article{DE_1977_13_6_a22,
     author = {Yu. A. Pykh},
     title = {Differential systems with non-negative normed solutions},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1138--1140},
     publisher = {mathdoc},
     volume = {13},
     number = {6},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_6_a22/}
}