1. Clifford, W.K. (1873) Preliminary sketch of bi-quaternions. Proceedings of London Mathematical Society, 4, 361?395
2. Study, E. (1903) Geometrie der Dynamen. Leipzig
3. McAulay, A. (1898) Octonions?A Development of Clifford's Bi-quaternions. Cambridge University Press
4. Dimentberg, F.M. (1950) The Determination of the Positions of Spatial Mechanisms. Izdatel'stvo Akademii Nauk, Moscow
5. Denavit, J. (1958) Displacement analysis of mechanisms based on (2×2) matrices of dual numbers. VDI-Berichte, 29, 81?89