@article{BenhammadiNicolasSchaub1998,
  author    = {Benhammadi, Farid and Nicolas, Pascal and Schaub, Torsten H.},
  title     = {Extension calculus and query answering in prioritized default logic},
  isbn      = {3-540-64993-X},
  year      = {1998},
  language  = {en}
}
@article{BenhammadiNicolasSchaub1998,
  author    = {Benhammadi, Farid and Nicolas, Pascal and Schaub, Torsten H.},
  title     = {Extension calculus and query answering in prioritized default logic},
  isbn      = {3-540- 64993-X},
  year      = {1998},
  language  = {en}
}
@article{BenhammadiNicolasSchaub1999,
  author    = {Benhammadi, Farid and Nicolas, Pascal and Schaub, Torsten H.},
  title     = {Query-answering in prioritized default logic},
  isbn      = {3-540-66131-X},
  year      = {1999},
  language  = {en}
}
@article{BenhammadiNicolasSchaub1999,
  author    = {Benhammadi, Farid and Nicolas, Pascal and Schaub, Torsten H.},
  title     = {Query-answering in prioritized default logic},
  isbn      = {3-540-66131-X},
  year      = {1999},
  language  = {en}
}