1. McGraw-Hill Series in Higher Mathematics;L.V. Ahlfors,1973
2. Ahlfors, L.V.: Möbius Transformations in Several Dimensions. University of Minnesota School of Mathematics, Minneapolis (1981)
3. Ahlfors, L.V.: Old and new in Möbius groups. Ann. Acad. Sci. Fenn., Ser. A 1 Math. 9, 93–105 (1984)
4. Barrett, J.F.: Hyperbolic geometry in special relativity. In: Duffy, M.C., Wegener, M.T. (eds.) Recent Advances in Relativity Theory. Proceedings, pp. 27–34. Hadronic Press, Palm Harbor (2000)
5. Belloni, L., Reina, C.: Sommerfeld’s way to the Thomas precession. Eur. J. Phys. 7, 55–61 (1986)