1. See, for instance, Y.P. Kuang, S.F. Tuan, T.M. Yan: in Proceedings of the Second International Conference on Hadron Spectroscopy (KEK, Japan, 1987); R.H. Dalitz, S.F. Tuan: in Proceedings of the Tenth Hawaii Conference in High Energy Physics. (Univ. of Hawaii Press, 1985)
2. K. Gottfried: in Proceedings of the International Symposium on Lepton and Photon Interactions at High Energy (Hamburg, 1977); Phys. Rev. Lett. 40 (1978) 598; G. Bhanot, W. Fischler, S. Rudaz: Nucl. Phys. B 155 (1979) 208; M.E. Peskin: ibid Nucl. Phys. B156 (1979) 365; G. Bhanot, M.E. Peskin: ibid Nucl. Phys. B 156 (1979) 391; K. Shizuya: Phys. Rev. D 22 (1980) 1180
3. T.M. Yan: Phys. Rev. D22 (1980) 1652
4. Y.P. Kuang, T.M. Yan: Phys. Rev. D24 (1981) 2847
5. S.-H.H. Tye: Phys. Rev. D13 (1976) 3416; R.C. Giles, S.-H.H. Tye: Phys. Rev. Lett. 37 (1976) 1175; Phys. Rev. D16 (1977) 1079