Tyshkevich DL, Karpenko II. On self-adjontness of 1-D Schrödinger operators with $\delta$-interactions. MFAT [Internet]. 2012 Dec. 25 [cited 2025 Dec. 16];18(4):360-72. Available from: https://zen.imath.kiev.ua/index.php/mfat/article/view/527