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@article{DE_1980_16_4_a9, author = {V. P. Fedotov}, title = {The extremum principle for a system of equations}, journal = {Differencialʹnye uravneni\^a}, pages = {679--683}, publisher = {mathdoc}, volume = {16}, number = {4}, year = {1980}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1980_16_4_a9/} }
V. P. Fedotov. The extremum principle for a system of equations. Differencialʹnye uravneniâ, Tome 16 (1980) no. 4, pp. 679-683. http://geodesic.mathdoc.fr/item/DE_1980_16_4_a9/