Harmonic analysis of Abelian inner automorphism groups of von Neumann algebras. Herbert Halpern — 1982 Mathematica Scandinavica
Spectra of operator equations and automorphism groups of von Neumann algebras. Herbert Halpern — 1978 Mathematica Scandinavica
Compact Operators in Type III... and Type III... Factors. Herbert Halpern; Victor Kaftal Mathematische Annalen