1. N. Isgur: Proc Int. Conf on High Energy Physics, Dallas USA, Ed. J.R. Sanford AIP Conf. Proc. 272 Vol 1 (1992) p. 33; D.V. Bugg: Proc. Int. Europhysics Conf. on High Energy Physics, Marseille, France, Eds. J Carr, M Perrottet: Editions Frontiers (1994) p. 717; C. Amsler: Int. Conf on High Energy Physics, Glasgow 20–26 July 1994. Plenary talk, Zürich preprint UZH-PH-50/94
2. R.P. Feynman: Photon Hadron Interactions, W.A. Benjamin Inc., Reading Mass. USA, (1972), pages 58 and 95; A. Katz, H.J. Lipkin: Phys. Lett. 7 (1963) 44; H.J. Lipkin: Phys. Lett. 72B (1977) 249; G.F. Chew: The Analytic S-Matrix, W.A. Benjamin Inc., New. York, 1966; G.F. Chew, C. Rosenzweig: Phys. Rep. 41 (1978) 264; G. Fogli, G. Preparata: Nuovo Cimento 48A (1978) 235; A.C.A. Maciel, J. Paton: Nucl. Phys B181 (1981) 277; A.W. Thomas et al.: Phys. Rev. D24 ((1981) 2161; E. Van Beveren et al.: Phys. Rev. D21 (1980) 773; D27 (1973) 1527; Z. Phys. C19 (1983) 275
3. J. Weinstein, N. Isgur: Phys. Rev. Lett. D48 (1982) 659; Phys. Rev D27 (1983) 588
4. CBAR collaboration, C. Amsler et al.: Phys. Lett. B333 (1994) 277
5. M. Boutemeur: Hadron 89 conf. proc. (Ajaccio, Corsica) p. 119