@article {2017, title = {Krein-Visik-Birman self-adjoint extension theory revisited}, number = {SISSA;25/2017/MATE}, year = {2017}, abstract = {The core results of the so-called KreIn-Visik-Birman theory of self-adjoint extensions of semi-bounded symmetric operators are reproduced, both in their original and in a more modern formulation, within a comprehensive discussion that includes missing details, elucidative steps, and intermediate results of independent interest.}, url = {http://preprints.sissa.it/handle/1963/35286}, author = {Matteo Gallone and Alessandro Michelangeli and Andrea Ottolini} }