@InProceedings{Atkinson:2001:UML,
  author =       "Colin Atkinson and Thomas K{\"u}hne",
  title =        "The Essence of Multilevel Metamodeling",
  pages =        "19--33",
  booktitle =    "UML 2001 - The Unified Modeling Language. Modeling
                            Languages, Concepts, and Tools. 4th
                  International Conference, Toronto, Canada, October 2001,
                  Proceedings",
  editor =       "Martin Gogolla and Cris Kobryn",
  publisher =    "Springer",
  series =       "LNCS",
  volume =       "2185",
  year =         "2001",
}