@article{DE_1991_27_2_a10,
     author = {K. B. Sabitov},
     title = {Maximum modulus principles for some classes of second-order elliptic and hyperbolic systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {272--278},
     publisher = {mathdoc},
     volume = {27},
     number = {2},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1991_27_2_a10/}
}