@article{DAN_1969_189_2_a2,
     author = {G. M. Vainikko},
     title = {Compact approximation of operators and approximate solution of operator equations},
     journal = {Doklady Akademii Nauk},
     pages = {237--240},
     publisher = {mathdoc},
     volume = {189},
     number = {2},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_189_2_a2/}
}