[1]
H. M. Pipa and O. G. Storozh, “On some perturbations changing the domain of proper extension of positively definite operator”, MFAT, vol. 11, no. 3, pp. 257–269, Sep. 2005, Accessed: Dec. 16, 2025. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/284