1. J.J. Aubert et al, Phys. Rev. Lett. 33, 1404 (1974); J.E. Augustin et al, Phys. Rev. Lett. 33, 1406 (1974).
2. A. Carrol et al, Phys. Lett. 61B, 303 (1976). Also, private communication from W. Baker of the BNL-FNAL-Rockefeller Collaboration.
3. Private communication from H. Kobrak of the Chicago-San Diego-Wisconsin Collaboration.
4. A.V. Barnes et al, Phys. Rev. Letts. 37, 76 (1976). See also 0.I. Dahl et al, Phys. Rev. Letts. 37, 80 (1976) for a study of Tr-p} ran.
5. J. Whitmore in Particles and Fields APS/DPF Meeting in Seattle (1975). H. Lubatti and P. Mockett eds. See also the comprehensive review of bubble chamber data by J. Whitmore, MSU Report (Feb. 1976) to appear in Physics Reports.