@article{MZM_1968_4_2_a8,
     author = {V. M. Millionshchikov},
     title = {A~criterion for a small change in the direction of the solutions of a~linear system of differential equations as the result of small disturbances in the coefficients of the system},
     journal = {Matemati\v{c}eskie zametki},
     pages = {173--180},
     publisher = {mathdoc},
     volume = {4},
     number = {2},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1968_4_2_a8/}
}