1. A.M. Stefanini et al., Report LNL-INFN(REP) 120/97, 1997
2. Annual Report 1999 of the Laboratori Nazionali di Legnaro, LNL-INFN(REP)-160/00, and references therein
3. SPES Project Study, LNL-INFN(REP) 145/99
4. G. Montagnoli et al., Nucl. Instrum. Methods A, in press
5. G. Montagnoli et al., in: Ref. [2], p. 160