1. B. Jouvet:Compt. Rend. Ac. Sci.,237, 1642 (1953);Journ. de Math.,33, 201 (1954) orThèse de doctorat, Paris (1954).
2. B. Jouvet:Suppl. Nuovo Cimento,2, 941 (1955);Reports Pisa Conf., Suppl. Nuovo Cimento (in print) (1956).
3. A. Salam:Phys. Rev.,84, 427 (1951).
4. B. Jouvet:Nuovo Cimento,3, 1133 (1956).
5. I am very indebted to Dr.V. Glaser for many interesting discussions on the unstable particles problem that he treated in detail in the case of Lee Model (Colloquium, October 31st, 1955, Copenhagen).