@article{DAN_1961_137_4_a1,
     author = {I. V. Gel'man},
     title = {Equivalence of some unbounded operators in {Banach} space},
     journal = {Doklady Akademii Nauk},
     pages = {764--767},
     publisher = {mathdoc},
     volume = {137},
     number = {4},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_137_4_a1/}
}