T ∗ T always has a positive selfadjoint extension

Operational calculus of linear relations

Richard Arens · Pacific Journal of Mathematics · 1961 · 370 citations · Full text

Spectral Theory, Infinite Dimensional Analysis, Topological Semigroups +12

Positive selfadjoint extensions of positive symmetric operators

Tsuyoshi Andô, Katsuyoshi Nishio · Tohoku Mathematical Journal · 1970 · 145 citations · Full text

Topological Semigroups, Linear Operator, Norm (Mathematics) +2

OPERATOR EXTENSIONS ON HILBERT SPACE

Vilmos Prokaj · 1998 · 25 citations

Spectral Theory, Linear Operator, Engineering +2

On products of unbounded operators

Zoltán Sebestyén, Jan Stochel · Acta Mathematica Academiae Scientiarum Hungaricae · 2003 · 14 citations · Full text

On suboperators with codimension one domains

Zoltán Sebestyén, Jan Stochel · Journal of Mathematical Analysis and Applications · 2009 · 14 citations · Full text

Domain Theory, Automated Reasoning, Set-theoretic Topology +2