@article{BesnardMercerSchaub2003,
  author    = {Besnard, Philippe and Mercer, Robert E. and Schaub, Torsten},
  title     = {Optimality theory throught default logic},
  isbn      = {3-540-20059-2},
  year      = {2003},
  language  = {en}
}
@article{DelgrandeGharibMerceretal.2003,
  author    = {Delgrande, James Patrick and Gharib, Mona and Mercer, Robert E. and Risch, V. and Schaub, Torsten},
  title     = {Lukaszewicz-style answer set programming : a preliminary report},
  issn      = {1613-0073},
  year      = {2003},
  language  = {en}
}