@article{DAN_1973_209_4_a2,
     author = {M. A. Gol'dman and S. N. Krachkovskii},
     title = {On the stability of some properties of a closed linear operator},
     journal = {Doklady Akademii Nauk},
     pages = {769--772},
     publisher = {mathdoc},
     volume = {209},
     number = {4},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1973_209_4_a2/}
}