@Unpublished{R28,
  key    =       {R28},
  author = 	 {Manfred Pinkal and J{\"o}rg Siekmann and Christoph Benzm{\"u}ller},
  title = 	 {DIALOG: Tutorial Dialog with an Assistance System for Mathematics},
  note = 	 {Project report in the Collaborative Research Centre SFB 378 on Resource-adaptive Cognitive Processes},
  pages =        {1--24},
  year =	 2004,
  url =		 {www.ags.uni-sb.de/~chris/papers/R28.pdf}
}