1. J. Ellis, Grand unified theories, CERN preprint TH-2942 (1980), in Scottish Universities Summer School in Physics, eds. K.C. Bowler and E.G. Sutherland (Univ. Edinburgh, 1981), p. 201
2. D.A. Ross, Phenomenology of unified gauge theories, CERN preprint TH-3174 (1981) and The calculation of the decay rate of the proton, CalTech report Calt 68779/C1 (1980)
3. M.B. Gavela et al., Phys. Rev. D 23, 1580 (1981)
4. G. Kane and G. Karl, Branching ratios in baryon decay, Michigan University internal report (1980)
5. J.F. Donoghue, Phys. Lett. 92B, 99 (1980)