@article{DAN_1960_132_5_a13,
     author = {V. \`E. Lyantse},
     title = {Conditions for closedness of the contraction of a self-adjoint operator},
     journal = {Doklady Akademii Nauk},
     pages = {1023--1026},
     publisher = {mathdoc},
     volume = {132},
     number = {5},
     year = {1960},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_132_5_a13/}
}