@article{DE_1966_2_3_a10,
     author = {S. G. Krein and G. I. Laptev},
     title = {Boundary value problems for second order differential equations in a {Banach} space. {I}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {382--390},
     publisher = {mathdoc},
     volume = {2},
     number = {3},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_3_a10/}
}