@article{10_4171_dm_196,
     author = {D.H. Jakubassa-Amundsen},
     title = {Localization of the essential spectrum for relativistic $N$-electron ions and atoms},
     journal = {Documenta mathematica},
     pages = {417--445},
     year = {2005},
     volume = {10},
     doi = {10.4171/dm/196},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/196/}
}