@article{SM_1968_5_3_a2,
     author = {L. N. Vaserstein},
     title = {The congruence problem for a unitary group of rank $\ge2$},
     journal = {Sbornik. Mathematics},
     pages = {351--355},
     year = {1968},
     volume = {5},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1968_5_3_a2/}
}