@article{BrungsGraeter2000,
  author    = {Brungs, Hans and Gr{\"a}ter, Joachim},
  title     = {Trees and Valuation Rings},
  year      = {2000},
  language  = {en}
}
@article{GraeterKlein2000,
  author    = {Gr{\"a}ter, Joachim and Klein, Markus},
  title     = {The Principal Axis Theorem for Holomorphic Functions},
  year      = {2000},
  language  = {en}
}