Hag, K., and M. Näätänen. “On the Outer Coefficient of Quasiconformality of a Cylindrical Map of a Convex Dihedral Wedge”. Annales Fennici Mathematici, vol. 5, no. 1, Feb. 1980, pp. 125-30, doi:10.5186/aasfm.1980.0509.