1. L. O'Raifeartaigh:Phys. Rev.,139, B 1052 (1965); andPhys. Rev. Lett.,14, 332 (1965).
2. For an alternative proof seeP. Roman:Proc. of the Conference on Noncompact Groups in Particle Physics, Milwaukee, 1966. (An earlier version was given byP. Roman andC. J. Koh:Nuovo Cimento,39, 1015 (1965).
3. We have discussed, from other points of view, the possible role of the de Sitter group in the theory of elementary particles on previous occasions. See, for example,P. Roman andJ. J. Aghassi:Journ. Math. Phys., in press, and earlier papers quoted therein. See alsoP. Roman andJ. J. Aghassi:Nuovo Cimento,42 A 193 (1966).
4. We do not want to give a cosmological explanation of the origin of mass, and there is no need for that in the present context.
5. For the proof of this Lemma and its generalizations see ref. (2), For an alternative proof seeP. Roman:Proc. of the Conference on Noncompact Groups in Particle Physics, Milwaukee, 1966. (An earlier version was given byP. Roman andC. J. Koh:Nuovo Cimento,39, 1015 (1965), or preprint BU-EP-10-66.