1. A. S. Wightman:Phys. Rev.,101, 860 (1956).
2. For a list of references see for instanceR. Haag andB. Schroer:University of Illinois preprint (September 1961). See alsoK. Bardakci:Thesis, University of Rochester (1961).
3. H. J. Borchers:Nuovo Cimento,15, 784 (1960).
4. O. W. Greenberg:M.I.T. preprint (July 1961).
5. G. F. Dell’Antonio:Northwestern University preprint (1961).