@article{DE_1971_7_3_a22,
     author = {S. L. Sobolev and S. A. Gal'pern and E. M. Landis},
     title = {Ivan {Georgevi{\v{c}}} {Petrovski{\v\i}} {(On} his seventieth birthday)},
     journal = {Differencialʹnye uravneni\^a},
     pages = {553--564},
     publisher = {mathdoc},
     volume = {7},
     number = {3},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_3_a22/}
}