@article{DAN_1986_287_3_a8,
     author = {M. E. Lerner},
     title = {Maximum principles for equations of hyperbolic and mixed types in},
     journal = {Doklady Akademii Nauk},
     pages = {550--554},
     publisher = {mathdoc},
     volume = {287},
     number = {3},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1986_287_3_a8/}
}