@InProceedings{Gogolla:1998:CQU,
  author =       "Martin Gogolla and Mark Richters",
  title =        "On Constraints and Queries in {UML}",
  pages =        "109--121",
  booktitle =    "The Unified Modeling Language -- Technical Aspects and
                  Applications",
  editor =       "Martin Schader and Axel Korthaus",
  publisher =    "Physica-Verlag, Heidelberg",
  year =         "1998",
}