Coordinatization of projective planes by special planar ternary rings Dalibor Klucký, Libuše Marková (1997) Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica
Correction to "On a functional equation arising from hyperbolic geometry", Volume 21 (1980), 113-116. Walter Benz (1981) Aequationes mathematicae