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@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/} }
V. G. Boltyanskii. The maximum principle, black holes and quasars. Differencialʹnye uravneniâ, Tome 15 (1979) no. 10, pp. 1888-1890. http://geodesic.mathdoc.fr/item/DE_1979_15_10_a15/