Efficient presentations of the group $\mathrm{PSL}(2, Z_n) \times \mathrm{PSL}(2, Z_m)$, for certain $n$, $m$.

Vatansever, B. (1997). Efficient presentations of the group $\mathrm{PSL}(2, Z_n) \times \mathrm{PSL}(2, Z_m)$, for certain $n$, $m$. MATHEMATICA SCANDINAVICA, 80, 188–194. https://doi.org/10.7146/math.scand.a-12618