@article{DAN_1957_116_5_a6,
     author = {I. V. Ostrovskii},
     title = {A generalization of a theorem stated by {M.\,G.~Krein}},
     journal = {Doklady Akademii Nauk},
     pages = {742--745},
     publisher = {mathdoc},
     volume = {116},
     number = {5},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_116_5_a6/}
}