@article{DAN_1964_154_5_a4,
     author = {M. G. Krein},
     title = {A new application of the fixed-point principle in the theory of operators in a space with indefinite metric},
     journal = {Doklady Akademii Nauk},
     pages = {1023--1026},
     publisher = {mathdoc},
     volume = {154},
     number = {5},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_154_5_a4/}
}