@InProceedings{Schmidt01:UQF,
  author = 	 {J.~Schmidt and H.~Niemann},
  title = 	 {{Using Quaternions for Parametrizing 3--D Rotations in Unconstrained Nonlinear Optimization}},
  booktitle = 	 {Vision, Modeling, and Visualization 2001},
address = {Stuttgart, Germany},
  pages = 	 {399-406},
  year = 	 {2001},
  editor = 	 {T.~Ertl and B.~Girod and G.~Greiner and H.~Niemann and H.--P.~Seidel},
 OPTmonth = 	 {November},
  isbn = {3-89838-028-9},
  publisher = {AKA/IOS Press, Berlin, Amsterdam},
  keywords = {Bild}
}