@article{DE_1977_13_6_a21,
     author = {I. I. Martynov},
     title = {Systems with a piecewise constant matrix of coefficients},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1135--1137},
     publisher = {mathdoc},
     volume = {13},
     number = {6},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_6_a21/}
}