直交群
↑ Hatcher, Allen (2002). Algebraic Topology. Cambridge University Press. pp. 293–294. ISBN 0-521-79160-X. Zbl 1044.55001
↑ Wilson, Robert A. (2009). The Finite Simple Groups. Graduate Texts in Mathematics. 251. London: Springer. pp. 69–75. ISBN 978-1-84800-987-5. Zbl 1203.20012