@InProceedings{Richters:1999:UML,
  author =       "Mark Richters and Martin Gogolla",
  title =        "A Metamodel for {OCL}",
  pages =        "156--171",
  booktitle =    "UML'99 - The Unified Modeling Language. Beyond the
                  Standard. Second International Conference, Fort Collins,
                  CO, USA, October 28-30. 1999, Proceedings",
  editor =       "Robert France and Bernhard Rumpe",
  publisher =    "Springer",
  series =       "LNCS",
  volume =       "1723",
  year =         "1999",
}