GÁBOS, Zoltán, and Ágnes MESTER. “Lines in the Three-Dimensional Bolyai-Lobachevskian Hyperbolic Geometry”. Studia Universitatis Babeș-Bolyai Mathematica, vol. 60, no. 4, Dec. 2015, pp. 583-95, https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/5835.