@phdthesis{Witt2003,
  author    = {Witt, Ingo},
  title     = {Beitr{\"a}ge zur Theorie singul{\"a}rer hyperbolischer Differentialoperatoren},
  address   = {Potsdam},
  pages     = {121 S.},
  year      = {2003},
  language  = {de}
}