1. Arcidiacono, G. (1973).Relatività e Cosmologia, Veschi, Roma.
2. Arcidiacono, G. (1976).Gen. Rel. Grav.,7, 885; (1977).Ibid.,8, 865; (1978).Ibid., 9, 949; (1979).Ibid., 10, 445.
3. Gürsey, F. (1964). ?Introduction to the de Sitter Group,? in F. Gürsey (ed.),Group Theoretical Concepts and Methods in Elementary Particle Physics, Gordon and Breach, London, pp. 365?389.
4. Arcidiacono, G. (1968).Collectanea Mathematica,19, 177.