The essential spectrum of relativistic one-electron ions in the Jansen-Hess model. Jakubassa-Amundsen, D.H. — 2002 Mathematical Physics Electronic Journal [electronic only]
Localization of the essential spectrum for relativistic N -electron ions and atoms. Jakubassa-Amundsen, D.H. — 2005 Documenta Mathematica
The projected single-particle Dirac operator for Coulombic potentials. Jakubassa-Amundsen, D.H. — 2005 Documenta Mathematica
On the essential spectrum of the Jansen-Hess operator for two-electron ions. Jakubassa-Amundsen, D.H. — 2008 Mathematical Physics Electronic Journal [electronic only]