@Inproceedings{Stumme1999acquiring,
  author = {Stumme, Gerd},
  title  = {Acquiring Expert Knowledge for the Design of Conceptual Information Systems},

  year   = {1999},
  number = {},
  url    = {http://www.kde.cs.uni-kassel.de/stumme/papers/1999/P1997-EKAW99.pdf},

  const  = {\ text}
}
@Inproceedings{stumme99dual,
  author = {Stumme, Gerd},
  title  = {Dual Retrieval in Conceptual Information Systems},

  year   = {1999},
  number = {},
  url    = {http://www.kde.cs.uni-kassel.de/stumme/papers/1999/P2021-BTW99.pdf},

  const  = {\ text}
}
@Inproceedings{stumme99numerical,
  author = {Stumme, G. and Wolff, K. E.},
  title  = {Numerical Aspects in the Data Model of Conceptual Information Systems},

  year   = {1999},
  number = {},
  url    = {http://www.kde.cs.uni-kassel.de/stumme/papers/1998/ER98.pdf},

  const  = {\ text}
}