@article{DAN_1988_298_4_a11,
     author = {L. B. Rapoport},
     title = {Sign-definiteness of a quadratic form under quadratic constraints},
     journal = {Doklady Akademii Nauk},
     pages = {822--826},
     year = {1988},
     volume = {298},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1988_298_4_a11/}
}