@article{DAN_1963_152_1_a8,
     author = {M. G. Krein and G. K. Langer},
     title = {On the spectral function of a self-adjoint operator in a space with indefinite metric},
     journal = {Doklady Akademii Nauk},
     pages = {39--42},
     publisher = {mathdoc},
     volume = {152},
     number = {1},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_152_1_a8/}
}