1. D. R. Botterill, D. W. Braben, R. Kikuchi, P. R. Norton, A. Del Guerra, A. Giazotto, M. A. Giorgi andA. Stefanini: DNPL/P158, submitted toPhys. Lett.
2. L. N. Hand:Phys. Rev.,129, 1834 (1963).
3. Yung-Su Tsai: SLAC-PUB-848.
4. CERN Computer Porogram Library, Program Minuit.
5. G. von Gehlen andH. Wessel: Bonn University Report PI-2-94 (1971).