R. G. Sanati, E. Ansari-piri, and M. Kardel, “Operators preserving orthogonality on Hilbert $\it{K}(H)$-modules”, MFAT, vol. 25, no. 2, pp. 189–194, Jun. 2019, Accessed: Dec. 15, 2025. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/722