@article{DE_1969_5_6_a6,
     author = {\`E. A. Tikhonova},
     title = {An analogy between the solutions of perturbed and unperturbed systems and the completeness of a divided diagonal matrix},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1037--1054},
     publisher = {mathdoc},
     volume = {5},
     number = {6},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1969_5_6_a6/}
}