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@article{DE_1985_21_2_a5, author = {O. I. Nikonov}, title = {Some extremal properties of observable differential systems}, journal = {Differencialʹnye uravneni\^a}, pages = {236--240}, publisher = {mathdoc}, volume = {21}, number = {2}, year = {1985}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1985_21_2_a5/} }
O. I. Nikonov. Some extremal properties of observable differential systems. Differencialʹnye uravneniâ, Tome 21 (1985) no. 2, pp. 236-240. http://geodesic.mathdoc.fr/item/DE_1985_21_2_a5/