@article{SM_1971_15_1_a0,
     author = {D. D. Sokolov},
     title = {On some properties of an indefinite metric},
     journal = {Sbornik. Mathematics},
     pages = {1--6},
     publisher = {mathdoc},
     volume = {15},
     number = {1},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1971_15_1_a0/}
}