双複素数
↑ Davenport, Clyde M. (1978). An Extension of the Complex Calculus to Four Real Dimensions, with an Application to Special Relativity (M.S.). Knoxville, Tennessee: University of Tennessee, Knoxville.
↑ Davenport, Clyde M. (1991) (英語). A Hypercomplex Calculus with Applications to Special Relativity. Knoxville, Tennessee: University of Tennessee, Knoxville. ISBN 0962383708
↑ Davenport, Clyde M. (2008), Commutative Hypercomplex Mathematics, オリジナルの2015-10-02時点におけるアーカイブ。, https://web.archive.org/web/20151002102049/http://home.comcast.net/~cmdaven/hyprcplx.htm
↑ Pei, Soo-Chang; Chang, Ja-Han; Ding, Jian-Jiun (2004-06-21). “Commutative reduced biquaternions and their Fourier transform for signal and image processing”.