@Article{LutzWaltherJANCL05,
  author =       "C. Lutz and D. Walther",
  title =        "PDL with Negation of Atomic Programs",
  journal =      "Journal of Applied Non-Classical Logic",
  year =         {2005},
  volume =       "15",
  number =       "2",
  pages =        "189--214"
}