@article{AA_1990_2_5_a0,
     author = {S. G. Krein and A. I. Tovbis},
     title = {Linear singular differential equations in finite-dimensional and {Banach} spaces},
     journal = {Algebra i analiz},
     pages = {1--62},
     publisher = {mathdoc},
     volume = {2},
     number = {5},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AA_1990_2_5_a0/}
}