@article{DAN_1990_315_6_a5,
     author = {N. N. Tarkhanov},
     title = {Approximation in {Sobolev} spaces by solutions of elliptic systems},
     journal = {Doklady Akademii Nauk},
     pages = {1308--1313},
     publisher = {mathdoc},
     volume = {315},
     number = {6},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_315_6_a5/}
}