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@article{DE_1986_22_2_a18, author = {V. M. Filippov}, title = {The variational principle for hypoelliptic equations with constant coefficients}, journal = {Differencialʹnye uravneni\^a}, pages = {338--343}, publisher = {mathdoc}, volume = {22}, number = {2}, year = {1986}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1986_22_2_a18/} }
V. M. Filippov. The variational principle for hypoelliptic equations with constant coefficients. Differencialʹnye uravneniâ, Tome 22 (1986) no. 2, pp. 338-343. http://geodesic.mathdoc.fr/item/DE_1986_22_2_a18/