Petunin, Y.I. and Tupko, N.P. (1999) “Theory of quadratic estimates of variance”, Ukrains’kyi Matematychnyi Zhurnal, 51(9), pp. 1217–1231. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4718 (Accessed: 14 April 2025).