@book{Witte2015,
  author    = {Witte, Hermann},
  title     = {Ist der Euro sicher?},
  publisher = {Lit},
  address   = {M{\"u}nster},
  isbn      = {978-3-643-13280-2},
  series    = {Lingener Studien zu Management und Technik},
  number    = {5},
  pages     = {177},
  year      = {2015},
  language  = {de}
}
@book{Witte2015,
  author    = {Witte, Hermann},
  title     = {Sustainable market economy},
  publisher = {Lit},
  address   = {M{\"u}nster},
  isbn      = {978-3-643-90656-4},
  series    = {Lingener Studien zu Management und Technik},
  number    = {3},
  pages     = {178},
  year      = {2015},
  language  = {en}
}