A. A. Yusenko and V. I. Rabanovich, “On decompositions of the identity operator into a linear combination of orthogonal projections”, MFAT, vol. 16, no. 1, pp. 57–68, Mar. 2010, Accessed: Dec. 16, 2025. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/440