1. Tuval Foguel and Abraham A. Ungar, Involutory decomposition of groups into twisted subgroups and subgroups, J. Group Theory 3 (2000), no. 1, 27–46.[MR]
  2. Tuval Foguel and Abraham A. Ungar, Gyrogroups and the decomposition of groups into twisted subgroups and subgroups, Pacific J. Math. 197 (2001), no. 1, 1–11.[MR]
  3. A. A. Ungar, Hyperbolic trigonometry in the Einstein relativistic velocity model of hyperbolic geometry, Comput. Math. Appl. 40 (2000), no. 2-3, 313–332.[MR]
  4. Abraham A. Ungar, Beyond the Einstein Addition Law and its Gyroscopic Thomas Precession, Fundamental Theories of Physics, vol. 117, Kluwer Academic Publishers Group, Dordrecht, 2001, pp. xlii+413.[MR/link]