@article{Baumgaertel1998,
  author    = {Baumg{\"a}rtel, Hellmut},
  title     = {Erhard Schmidt, John von Neumann},
  isbn      = {3-7643-5943- 9},
  year      = {1998},
  language  = {de}
}
@article{Baumgaertel1993,
  author    = {Baumg{\"a}rtel, Hellmut},
  title     = {Laudatio Hans Kaiser},
  year      = {1993},
  language  = {de}
}