1. G. Carron et al., Phys. Lett. 77B, 353 (1978).
2. M. Bell et al., Phys. Lett. 87B, 275 (1979).
3. C. Rubbia, On the feasibility of pp collisions in the SPS, CERN/EP Internal Report 77-1 (1977).
4. D.B. Cline, Proc. Berkeley Workshop pp Collisions, (LBL-7574, 1978), p. 31.
5. Design study for the pp colliding beam facility, CERN/PS/AA 78-3 (1978).