@article{MZ_1987__196_173889,
     author = {J. Mennicke and J. Elstrodt and F. Grunewald},
     title = {Vahlen's {Group} of {Clifford} {Matrices} and {Spin-Groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {369--390},
     publisher = {mathdoc},
     volume = {196},
     year = {1987},
     zbl = {0611.20027},
     url = {http://geodesic.mathdoc.fr/item/MZ_1987__196_173889/}
}