Bekker, M. B., M. J. Bohner, A. P. Ugolʹnikov, and H. D. Voulov. 2018. “Parametrization of Scale-Invariant Self-Adjoint Extensions of Scale-Invariant Symmetric Operators”. Methods of Functional Analysis and Topology 24 (1): 1-15. https://zen.imath.kiev.ua/index.php/mfat/article/view/679.