@article{DE_1985_21_9_a29,
     author = {A. D. Myshkis},
     title = {Theorems of {Sturm} type for linear systems of differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1639--1641},
     year = {1985},
     volume = {21},
     number = {9},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_9_a29/}
}