@conference{Per07c,
  title = "A Hierarchy of Quantum Semantics.",
  author = "S. Perdrix",
  year = "2007",
  booktitle = "Proceedings of the 3rd International Workshop on Development of Computational Models (to appear)",
  howpublished = "To appear in Proceedings of the 3rd International Workshop on Development of Computational Models",
  url = "http://www.pps.jussieu.fr/~danos/dcm07/pdf/perdrix.pdf",
}