@misc{Richter1991,
  author    = {Richter, Martin},
  title     = {Anhang, Pr{\"u}fung der Pflichtangaben zum Einzelabschluß},
  isbn      = {3-7910-8036-9},
  year      = {1991},
  language  = {de}
}
@misc{Richter2003,
  author    = {Richter, Martin},
  title     = {Accrual Prinzip},
  isbn      = {3-7890-6319-3},
  year      = {2003},
  language  = {de}
}