1. E. P. Wigner, in F. Gürsey (ed): Group Theoretical Concepts and Methods in Elementary Particle Physics. Gordon and Breach, New York, 1964, p. 37.
2. E. Artin, Geometric Algebra, Academic Press, New York, 1951, p. 88.
3. Proofs of the Wigner throrem can be found in lLudwing, (1954, p. 101)
4. U. Uhlhorn, Ark. Fys.
23, 307 (1963)
5. L. O’Raifeartaigh, G. Rasche, Ann. of Phys.
2b, 155 (1963);