@article{DE_1972_8_8_a20,
     author = {M. L. Gusakova},
     title = {Necessary optimality conditions for systems that are not solved with respect to the derivative},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1498--1500},
     publisher = {mathdoc},
     volume = {8},
     number = {8},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_8_a20/}
}