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@article{DE_1985_21_5_a25, author = {A. V. Lasunsky}, title = {On a small variation of the characteristic indices of a regular linear system}, journal = {Differencialʹnye uravneni\^a}, pages = {901--903}, publisher = {mathdoc}, volume = {21}, number = {5}, year = {1985}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1985_21_5_a25/} }
A. V. Lasunsky. On a small variation of the characteristic indices of a regular linear system. Differencialʹnye uravneniâ, Tome 21 (1985) no. 5, pp. 901-903. http://geodesic.mathdoc.fr/item/DE_1985_21_5_a25/