@article{FladFladHarutyunyanSchulze2018,
  author    = {Heinz-J{\"u}rgen Flad and Gohar Flad-Harutyunyan and Bert-Wolfgang Schulze},
  title     = {Ellipticity of the quantum mechanical Hamiltonians},
  journal   = {Journal of pseudo-differential operators and applications},
  series    = {corner singularity of the helium atom},
  volume    = {9},
  number    = {3},
  pages     = {451 -- 467},
  doi       = {10.1007/s11868-017-0201-4},
  year      = {2018},
}