@article{KUTGS_1976_9_a6,
     author = {V. G. Kopp},
     title = {Groups of infinitesimal revolutions of six-dimensional space of zero signature},
     journal = {Trudy Geometricheskogo Seminara},
     pages = {43--53},
     year = {1976},
     volume = {9},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/KUTGS_1976_9_a6/}
}