1. 1. H. F. Baker, Principles of geometry, vol. 1, 2d ed., Cambridge, 1929.
2. 1a. H. F. Baker, ibid, vol. 3, Cambridge, 1934.
3. Note to the preceding paper by C. V. H. Rao;Baker, H. F.;Proc. Cambridge Philos. Soc.,1946
4. Configurations harmoniques et quaternions;Benneton, Gaston;Ann. Sci. \'{E}cole Norm. Sup. (3),1947