@article{DE_1968_4_8_a13,
     author = {V. V. Martynov},
     title = {Direct methods for the qualitative spectral analysis of a nonselfadjoint system of first order differential equations. {I}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1494--1508},
     publisher = {mathdoc},
     volume = {4},
     number = {8},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_8_a13/}
}