@article{DE_1969_5_1_a13,
     author = {V. K. Romanko},
     title = {Systems with first order derivative in the ``time''},
     journal = {Differencialʹnye uravneni\^a},
     pages = {174--185},
     publisher = {mathdoc},
     volume = {5},
     number = {1},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1969_5_1_a13/}
}