P. Melik-Adamyan, “On Nagy-Foias Characteristic Function in Extensions Theory of Hermitian Operators”, Armen.J.Math., vol. 8, no. 1, pp. 1–24, Jun. 2016, Accessed: Apr. 04, 2025. [Online]. Available: https://armjmath.sci.am/index.php/ajm/article/view/120