@Article{fischer87,
  author = {Fisher, Douglas H.},
  title  = {Knowledge Acquisition Via Incremental Conceptual Clustering},
  journal = {Machine Learning},
  year   = {1987},
  number = {2},
  url    = {},

  const  = {\ text}
}
@Article{h1987knowledge,
  author = {Fisher, Douglas H.},
  title  = {Knowledge Acquisition Via Incremental Conceptual Clustering},
  journal = {Machine Learning},
  year   = {1987},
  number = {2},
  url    = {http://dx.doi.org/10.1023/A:1022852608280},

  const  = {\ text}
}