@misc{SponagelWachowitz1992,
  author    = {Sponagel, Stefan and Wachowitz, Waldemar},
  title     = {Shaft seal : United States Patent 5,143,385 ; date of patent: Sep. 1, 1992 / assignee: Firma Carl Freudenberg},
  publisher = {[United States Patent and Trademark Office]},
  address   = {[Alexandria, VA]},
  pages     = {5 S. : Ill.},
  year      = {1992},
  language  = {en}
}
@book{SponagelWachowitz1993,
  author    = {Sponagel, Stefan and Wachowitz, Waldemar},
  title     = {Wellendichtung : Europ{\"a}ische Patentschrift DE3621242C1 ; Ver{\"o}ffentlichungstag der Patentschrift : 06.06.1993 / Anmelder: Fa. Carl Freudenberg},
  publisher = {Europ{\"a}isches Patentamt},
  address   = {[M{\"u}nchen u.a.]},
  pages     = {5 S. : Ill.},
  year      = {1993},
  language  = {de}
}
@misc{SponagelWachowitz1990,
  author    = {Sponagel, Stefan and Wachowitz, Waldemar},
  title     = {Wellendichtung : Offenlegungsschrift DE3830706A1 ; Ver{\"o}ffentlichungstag im Patentblatt: 22.03.1990 / Anmelder: Fa. Carl Freudenberg},
  publisher = {Deutsches Patent- und Markenamt},
  address   = {M{\"u}nchen},
  pages     = {4 S. : Ill.},
  year      = {1990},
  language  = {de}
}