1. Witten, E., in G.'t Hooft et al. (ed.), Recent Developments in Gauge Theories, Plenum Press, N.Y., 1980; Coleman, S., in Pointlike Structures Inside and Outside Hadrons, Erice Lecture Notes, 1979; Migdal, A.A., Nucl. Phys. B(FS) (1981) (to appear);
2. Gervais, J.L. and Neveu, A., Preprint LPTENS 81/6, 1981; Olesen, P., Preprint Nordita NBI-HE-81-5, 1981.
3. Nissimov, E.R. and Pacheva, S.J., Lett. Math. Phys. 5, 67 (1981).
4. Jackiw, R. and Templeton, S., Phys. Rev. D23, 2291 (1981).
5. Appelquist, T. and Pisarski, R., Phys. Rev. D23 2305 (1981).