1. Segre, C.: \emph{The real representations of complex elements and extension to bicomplex}. Systems. Math. Ann., 40, 413, (1892).
2. Pei, S. C., Chang, J. H., Ding, J. J.: \emph{Commutative reduced biquaternions and their fourier transform for signal and image processing applications}. IEEE Trans. on Signal Proces., 52(7), 2012-2031, (2004).
3. Catoni, F., Boccaletti, D., Cannata, R., Catoni, V., Nichelatti, E., Zampetti, P.: \emph{The mathematics of minkowski space-time with an introduction to commutative hypercomplex numbers}. Birkhauser Verlag AG, Berlin, (2008).
4. Pei S., Chang J., Ding J., Chen M.: \emph{Eigenvalues and singular value decompositions of reduced biquaternion matrices}. IEEE Trans. Circ. Syst. I., 55(9), 1549-8328, (2008).
5. Isokawa, T., Nishimura, H., Matsui, N.: \emph{Commutative quaternion and multistate hopfield neural networks}. In Proc. Int. Joint Conf. Neural Netw., Barcelona, Spain, 1281-1286, (2010).