@article{10_4171_dm_241,
     author = {Sergey Morozov},
     title = {Essential spectrum of multiparticle {Brown-Ravenhall} operators in external field},
     journal = {Documenta mathematica},
     pages = {51--79},
     year = {2008},
     volume = {13},
     doi = {10.4171/dm/241},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/241/}
}