Petunin, Yu. I., and N. P. Tupko. “Theory of Quadratic Estimates of Variance”.
Ukrains’kyi Matematychnyi Zhurnal
51, no. 9 (September 25, 1999): 1217–1231. Accessed April 14, 2025.
https://umj.imath.kiev.ua/index.php/umj/article/view/4718
.