TY - RPRT T1 - Krein-Visik-Birman self-adjoint extension theory revisited Y1 - 2017 A1 - Matteo Gallone A1 - Alessandro Michelangeli A1 - Andrea Ottolini AB - 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. UR - http://preprints.sissa.it/handle/1963/35286 U1 - 35591 U2 - Mathematics ER -