The Friedrichs Extension of Singular Differential Operators

Formally self-adjoint quasi-differential operators

Anton Zettl · Rocky Mountain Journal of Mathematics · 1975 · 112 citations · Full text

Natural Sciences, Mathematics, Differential Equations +7

Singular Sturm-Liouville Problems: The Friedrichs Extension and Comparison of Eigenvalues

Heinz‐Dieter Niessen, Anton Zettl · Proceedings of the London Mathematical Society · 1992 · 102 citations

Natural Sciences, Mathematics, Differential Equations +16

A Characterization of the Friedrichs Extension of Sturm-Liouville Operators

Hubert Kalf · Journal of the London Mathematical Society · 1978 · 85 citations

Natural Sciences, Mathematics, Physics +13

The Friedrichs Extension of Singular Differential Operators

Marco Marletta, Anton Zettl · Journal of Differential Equations · 2000 · 47 citations

Natural Sciences, Mathematics, Differential Equations +13

Semi-boundedness of Ordinary Differential Operators

Manfred Möller, Anton Zettl · Journal of Differential Equations · 1995 · 39 citations

Natural Sciences, Mathematics, Differential Equations +9