@article{SM_1968_4_2_a1,
     author = {L. N. Vaserstein},
     title = {Subgroups of finite index of a spinor group of rank $\geqslant2$},
     journal = {Sbornik. Mathematics},
     pages = {161--166},
     publisher = {mathdoc},
     volume = {4},
     number = {2},
     year = {1968},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1968_4_2_a1/}
}