MATHEMATICA SCANDINAVICA, vol.80, no.2, pp.188-194, 1997 (SCI-Expanded)
We give deficiency -4 presentations of the groups PSL(2, Z(n)) x PSL(2, Z(m)), n, m odd numbers and [(n = 1(mod6) and m = 1(mod6)) or (n = 1(mod6) and m = -1(mod6)) or (n = 1(mod6) and m = -1(mod6)) or (n = -1(mod6) and m = 1(mod6))]. Moreover efficient presentations are given for certain cases of the groups considered.