@Article{kane-aij2004,
  author =       "K. Kaneiwa",
  title =        "Order-Sorted Logic Programming with Predicate Hierarchy",
  journal =      "Artificial Intelligence",
  volume =       "158",
  number =       "2",
  pages =        "155-188",
  publisher =    "Elsevier", 
  year   =       "2004"
}