1. Abraham A. Ungar, “Thomas rotation and the parametrization of the Lorentz transformation group.”Found Phys. Lett. 1, 57–89 (1988).
2. Abraham A. Ungar, “The Thomas rotation formalism underlying a nonassociative group structure for relativistic velocities.”Appl. Math. Lett. 1, 403–405 (1988).
3. Arlan Ramsay and Robert D. Richtmyer,Introduction to Hyperbolic Geometry (Springer, New York, 1995), p. 251.
4. Charles W. Misner, Kip S. Thorne, and John Archibald Wheeler,Gravitation, Box 2.4. pp. 67–68 (W. H. Freeman, San Francisco, 1973). See also Jean-Marc Levy-Leblond, “Additivity, rapidity, relativity”,Am. J. Phys. 47, 1045–1049 (1979); Isaac Moiseevich Yaglom,A Simple Non-Euclidean Geometry and Its Physical Basis: an Elementary Account of Galilean Geometry and the Galilean Principle of relativity, translated from the Russian by Abe Shenitzer with the editorial assistance of Basil Gordon (Springer, New York, 1979, and Arlan Ramsay and Robert D. Richtmyer,Introduction to Hyperbolic Geometry (Springer, New York, 1995).
5. Cornelius Lanczos,Space through the Ages. The Evolution of Geometrical Ideas from Pythagoras to Hilbert and Einstein (Academic Press, New York, 1970), p. 66.