@misc{SponagelGrafGross2007,
  author    = {Stefan Sponagel and G{\"u}nter Graf and Heinz Groß},
  title     = {Method for the manufacture of a sealing ring with a sealing lip having hydrodynamically acting return elements : United States Patent 4,850,097 ; date of patent: Jul. 25, 1989 / assignee: Firma Carl Freudenberg. Inventors: Gunter Graf ; Heinz Gross ; Stefan Sponagel},
  institution = {Fachbereich Medizintechnik und Technomathematik},
  type      = {patent},
  pages     = {4 S. : Ill.},
  year        = {2007},
}