@Article{koscli03b,
  author = "K. Konczak and T. Schaub and T. Linke",
  title = "Graphs and colorings for answer set programming with
                  preferences",
  journal = "Fundamenta Informaticae",
  year = 2003,
  volume = 57,
  number = "2-4",
  pages = "393-421"
}