@article{DE_1969_5_8_a19,
     author = {V. N. Laptinskii and V. V. Pugin},
     title = {First order nonlinear matrix-valued differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1523--1525},
     year = {1969},
     volume = {5},
     number = {8},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1969_5_8_a19/}
}