Connections the Sobolev spaces and the Hilbert space ℓ2 and their application at point interaction model

Yury Kovalev,. “Connections the Sobolev Spaces and the Hilbert Space ℓ2 and Their Application at point Interaction Model ”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 69, no. 12, July 2023, pp. 1615-24, https://umj.imath.kiev.ua/index.php/umj/article/view/6012.