Tukia, P., and X. Wang. “Discreteness of Subgroups of $\mathrm{SL}(2,\boldsymbol{C})$ Containing Elliptic Elements”. MATHEMATICA SCANDINAVICA, vol. 91, no. 2, Dec. 2002, pp. 214-20, doi:10.7146/math.scand.a-14386.