@article{DE_1993_29_10_a11,
     author = {V. M. Savchin},
     title = {On the structure of variational equations with symmetric operator $d/dt$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1765--1771},
     publisher = {mathdoc},
     volume = {29},
     number = {10},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1993_29_10_a11/}
}