@article{DE_1979_15_10_a15,
     author = {V. G. Boltyanskii},
     title = {The maximum principle, black holes and quasars},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1888--1890},
     publisher = {mathdoc},
     volume = {15},
     number = {10},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1979_15_10_a15/}
}