@article{DE_1989_25_7_a5,
     author = {Yu. V. Pokornyi and O. M. Penkin},
     title = {Comparison theorems for equations on graphs},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1141--1150},
     publisher = {mathdoc},
     volume = {25},
     number = {7},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_7_a5/}
}