[1]
“On connection between the norm of a sum of orthoprojections onto subspaces and the norm of the product of orthoprojections onto the corresponding orthogonal complements”, ЗПІМ, vol. 12, no. 1, pp. 178–184, May 2015, Accessed: Sep. 09, 2026. Available: https://trim.imath.kiev.ua/index.php/trim/article/view/13