1. S. Frullani and J. Mougey, Adv. Nucl. Phys. 14, 1 (1984)
2. S. Boffi, C. Giusti and F.D. Pacati, Phys. Rep. 226, 1 (1993)
3. J.F.J, van den Brand, Thesis, University of Amsterdam, 1988
4. J.F.J, van den Brand et al., Phys. Rev. Lett. 60, 2006 (1988)
5. J.F.J, van den Brand et al., Nucl. Phys. A534, 637 (1991)