1. F. Guérin and H.M. Fried, Phys. Rev. D33 (1986) 3039
2. H.M. Fried and T. Grandou, Phys. Rev. D33 (1986) 1151
3. H-T Cho, T. Grandou, and H.M. Fried, Phys. Rev. D37 (1988) 946 and 960
4. H.M. Fried and H-T Cho, Phys. Rev. D41 (1990) 1489
5. H.M. Fried, in Proceedings of the IXth Moriond Workshop, Les Arcs, France (January 1989 ).