@inproceedings{BoronatKnappMeseguerWirsing,
  author    = {Artur Boronat and Alexander Knapp and Jos\'{e} Meseguer and Martin Wirsing},
  title     = {{What is a Multi-Modeling Language?}},
  booktitle = {{19th International Workshop on Algebraic Development Techniques (WADT 2008)}},
  publisher = {Springer},
  series 	= {LNCS},
  volume    = {5486},
  pages =     {71--87},
  year      = {2009}
}