1. W. Kummer:Acta Phys. Austriaca,41, 315 (1975);W. Konetschny andW. Kummer:Nucl. Phys., 100 B, 106 (1975); 108 B, 397 (1976), contain a fairly exhaustive list of references.
2. R. Delbourgo, A. Salam andJ. Strathdee:Nuovo Cimento,23 A, 237 (1974).
3. P. Cvitanovio:Nucl. Phys.,130 B, 114 (1977);W. Konetschny:Nuovo Cimento,44 A, 465 (1978). See alsoJ. Frenkel andR. Meuldermans:Phys. Lett., 65 B, 64 (1976).
4. D. J. Gross andF. Wilczek:Phys. Rev.,8, 3633 (1973).
5. J. Frenkel andJ. C. Taylob:Nucl. Phys.,109 B, 526 (1976).