@article{DE_1983_19_3_a21,
     author = {I. V. Maiorov},
     title = {An extremum principle for a degenerate hyperbolic system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {532--535},
     publisher = {mathdoc},
     volume = {19},
     number = {3},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1983_19_3_a21/}
}