Dmytrenko, S. O., D. V. Kyurchev, and M. V. Pratsiovytyi. 2009. “$A_2$-Continued Fraction Representation of Real Numbers and Its Geometry”. Ukrains’kyi Matematychnyi Zhurnal 61 (4), 452-63. https://umj.imath.kiev.ua/index.php/umj/article/view/3033.