@article{DAN_1990_314_1_a23,
     author = {V. S. Mel'nik},
     title = {Extremal problems for operator-differential systems},
     journal = {Doklady Akademii Nauk},
     pages = {101--105},
     publisher = {mathdoc},
     volume = {314},
     number = {1},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_314_1_a23/}
}