@article{SchaubWang2001,
  author    = {Schaub, Torsten and Wang, Kewen},
  title     = {A comparative study of logic programs with preference},
  isbn      = {1-558-60777-3},
  issn      = {1045-0823},
  year      = {2001},
  language  = {en}
}
@article{SchaubWang2003,
  author    = {Schaub, Torsten and Wang, Kewen},
  title     = {A semantic framework for prefernce handling in answer set programming},
  year      = {2003},
  language  = {en}
}