@article{DE_1975_11_7_a21,
     author = {A. N. Kochubei},
     title = {The expansion in root vectors of abstract differential operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1341--1342},
     publisher = {mathdoc},
     volume = {11},
     number = {7},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_7_a21/}
}