@article{DAN_1968_179_5_a4,
     author = {G. M. Vainikko},
     title = {Similar operators},
     journal = {Doklady Akademii Nauk},
     pages = {1029--1031},
     publisher = {mathdoc},
     volume = {179},
     number = {5},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1968_179_5_a4/}
}