Rabanovych, V. I. “On the Decomposition of a Diagonal Operator into a Linear Combination of Idempotents or Projectors”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 3 (March 25, 2005): 388–393. Accessed May 25, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3606.