@article{DAN_1969_189_2_a8,
     author = {V. R. Portnov},
     title = {A certain projection operator of {S.\,L.~Sobolev} type},
     journal = {Doklady Akademii Nauk},
     pages = {258--260},
     publisher = {mathdoc},
     volume = {189},
     number = {2},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_189_2_a8/}
}