Finding a Minimum Medial Axis of a Discrete Shape is NP-hard

@article{dcoeurjo_MinMANP,
      author = {Coeurjolly, D. and Hulin, J. and Sivignon, I.},
      journal = {Theoretical Computer Science},
      language = {en},
      month = {October},
      publisher = {Elsevier},
      title = {Finding a Minimum Medial Axis of a Discrete Shape is NP-hard},
      url = {http://liris.cnrs.fr/publis/?id=3479},
      year = {2008}
}