1. T. W. Marshall:Proc. Cambridge Phil. Soc.,61, 537 (1965);T. H. Boyer:Phys. Rev.,182, 1374 (1969).
2. P. Braffort, M. Spighel andC. Tzara:Compt. Rend.,239, 157 (1954);P. Braffort andC. Tzara:Compt. Rend,239, 1779 (1954);P. Braffort, M. Surdin andA. Taroni:Compt. Rend.,261, 4339 (1965);P. Braffort:Compt. Rend.,270, 12 (1970). For a recent review, seeM. Surdin:Ann. Inst. H. Poincaré,15, 203 (1971).
3. T. W. Marshall:Proc. Roy. Soc., A276, 475 (1963);Proc. Camb. Phil. 61, 537 (1965);Nuovo Cimento,38, 206 (1965);E. Santos:Anales de Fisica,64, 317 (1968);T. H. Boyer:Phys. Rev.,174, 1631, 1764 (1968);180, 19 (1969);182, 1374 (1969);186, 1304 (1969);Phys. Rev. D,1, 1526, 2257 (1970).
4. P. Braffort andA. Taroni:Compt. Rend.,264, 1437 (1967);M. Surdin:Compt. Rend. 270, 193 (1970). See also ref. (2) andT. W. Marshall:Proc. Roy. Soc. A 276, 475 (1963);Proc. Camb. Phil.,61, 537 (1965);Nuovo Cimento,38, 206 (1965).
5. T. W. Marshall:Nuovo Cimento,38, 206 (1965);M. Surdin, P. Braffort andA. Taroni:Nature,210, 406 (1966);T. H. Boyer:Phys. Rev.,182, 1374 (1969);O. Theimer:Phys. Rev. D,4, 1597 (1971).