@article{ZVMMF_1969_9_4_a0,
     author = {G. M. Vainikko},
     title = {The compact approximation principle in the theory of approximation methods},
     journal = {\v{Z}urnal vy\v{c}islitelʹnoj matematiki i matemati\v{c}eskoj fiziki},
     pages = {739--761},
     publisher = {mathdoc},
     volume = {9},
     number = {4},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZVMMF_1969_9_4_a0/}
}