@article{DE_1985_21_10_a28,
     author = {S. G. Krein},
     title = {Singularly perturbed linear differential equations in a {Banach} space},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1814--1817},
     publisher = {mathdoc},
     volume = {21},
     number = {10},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_10_a28/}
}