@article{10695,
  author = {C. Cerjan and William Reinhardt and J. Avron},
  title = {Spectra of atomic Hamiltonians in DC fields: use of the numerical range to investigate the effect of a dilatation transformation},
  year = {1978},
  journal = {Journal of Physics B: Atomic and Molecular Physics},
  volume = {11},
  pages = {L201 - L205},
  month = {Feb-04-1979},
  issn = {0022-3700},
  doi = {10.1088/0022-3700/11/7/002},
}