Paper  bibtex   

@inproceedings{ kaschek_little_2004,
  title = {A little theory of abstraction.},
  url = {http://cs.emis.de/LNI/Proceedings/Proceedings45/GI-Proceedings.45-6.pdf},
  urldate = {2013-07-31},
  booktitle = {Modellierung},
  author = {Kaschek, Roland},
  year = {2004},
  pages = {75–92}
}