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@article{DE_1977_13_6_a14, author = {V. N. Vragov}, title = {On the theory of boundary value problems for equations of mixed type in space}, journal = {Differencialʹnye uravneni\^a}, pages = {1098--1105}, publisher = {mathdoc}, volume = {13}, number = {6}, year = {1977}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1977_13_6_a14/} }
V. N. Vragov. On the theory of boundary value problems for equations of mixed type in space. Differencialʹnye uravneniâ, Tome 13 (1977) no. 6, pp. 1098-1105. http://geodesic.mathdoc.fr/item/DE_1977_13_6_a14/