@article{Jonas1999,
  author    = {Jonas, Peter},
  title     = {On the trace formula of perturbation theory},
  year      = {1999},
  language  = {en}
}
@article{Jonas1998,
  author    = {Jonas, Peter},
  title     = {Operator representations of definitizable functions},
  year      = {1998},
  language  = {en}
}
@article{JonasLanger1993,
  author    = {Jonas, Peter and Langer, Heinz},
  title     = {Selfadjoint extensions of a closed linear relation of defect one in a Krein space},
  year      = {1993},
  language  = {en}
}