Twists - An operational representation of shape
 @InProceedings{sommer05lncs2,
  author = 	 {G. Sommer and B. Rosenhahn and C. Perwass},
  title = 	 {Twists - An operational representation of shape},
  booktitle = 	 {Computer Algebra and Geometric Algebra with Applications},
organization = 	 {6th International Workshop IWMM 2004, Shanghai, China and International Workshop GIAE 2004, Xian, China},
  publisher =	 {Springer-Verlag, Berlin Heidelberg},
  year =	 2005,
  editor =	 {H. Li  and P.J. Olver and G. Sommer},
  series =	 {LNCS},
  volume =     {3519},
  pages =      {278-297}
}