@article{DAN_1971_200_1_a0,
     author = {V. I. Arkin and V. L. Levin},
     title = {A variational problem with functions of several variables and operator restrictions: {The} maximum principle and existence theorem},
     journal = {Doklady Akademii Nauk},
     pages = {9--12},
     publisher = {mathdoc},
     volume = {200},
     number = {1},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_200_1_a0/}
}