@book{KnepperPfeiffer1999,
  author    = {Knepper, Ludger and Pfeiffer, Johann},
  title     = {Diplom-Ingenieur / Diplom-Ingenieurin (Fachhochschule) Maschinenbau, Energie- und W{\"a}rmetechnik},
  publisher = {Bertelsmann},
  address   = {Bielefeld},
  pages     = {Loseblattausg.},
  year      = {1999},
  language  = {de}
}
@book{GrundmannSchoenholtz1999,
  author    = {Grundmann, Reinhard and Sch{\"o}nholtz, Friedrich},
  title     = {„Ventilatoren-Fibel" der Firma Babcock-BSH},
  publisher = {Promotor-Verlag},
  address   = {Karlsruhe},
  year      = {1999},
  language  = {de}
}
@book{Schuermann1999,
  author    = {Sch{\"u}rmann, Wilhelm},
  title     = {Wohin kein Auge reicht : von der Entdeckung des Unsichtbaren / Konzeption: Wilhelm Sch{\"u}rmann},
  address   = {Hamburg},
  pages     = {185 S. : zahlr. Ill.},
  year      = {1999},
  language  = {de}
}
@book{BenknerDavid1999,
  author    = {Benkner, Thorsten and David, Klaus},
  title     = {Digitale Mobilfunksysteme : Grundlagen und aktuelle Systeme. - 2., aktualis. u. erw. Aufl.},
  publisher = {Teubner},
  address   = {Stuttgart},
  isbn      = {3-519-16181-8},
  pages     = {XIII, 457 S.. : graph. Darst.},
  year      = {1999},
  language  = {en}
}