Petunin, Y. I., and RublevВ. V. “Minimum-Area Ellipse Containing a Finite Set of Points. I”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 50, no. 7, July 1998, pp. 980–988, https://umj.imath.kiev.ua/index.php/umj/article/view/4877.