1. P. P. Kulish and L. D. Faddeev, Teor. Mat. Fiz.,4, 153 (1970).
2. C. A. Nelson, Nucl. Phys. B,181, 141 (1981).
3. C. A. Nelson, Nucl. Phys. B,186, 187 (1981).
4. J. Frenkel, J. C. Taylor, and A. Gatheral, Nucl. Phys. B,194, 172 (1982).
5. V. V. Bazhanov, G. P. Pron'ko, and Yu. G. Stroganov, ?Asymptotic states in a theory with non-Abelian symmetry,? Preprint OTF 76-113 [in Russian], Department of Theoretical Physics, Institute of High Energy Physics, Serpukhov (1976).