@article{DE_1972_8_5_a12,
     author = {S. G. Krein and Yu. B. Savchenko},
     title = {Exponential dichotomy for partial differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {835--844},
     publisher = {mathdoc},
     volume = {8},
     number = {5},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_5_a12/}
}