@inproceedings{ Liu03,
  ps = {http://www.cs.toronto.edu/cogrobo/Papers/liu03trac.ps}
}
,
  title = {A Tractability Result for Reasoning with Incomplete First-Order Knowledge Bases}
}
,
  url = {liu03trac.pdf}
}
,
  booktitle = {Proc. IJCAI-03}
}
,
  author = {Liu, Yongmei and Levesque, Hector}
}
,
  year = {2003}
}
,
  month = {August}
}
,
  key = {CogRobo}
}
,
  address = {Acapulco, Mexico}
}
,
  pages = {83--88}
}