@article{grps2004-48,

   author = "J. Hoffmann, J. Porteous, L. Sebastia",

   title = "Ordered Landmarks in Planning",

   journal = "Journal of Artificial Intelligence Research",

   publisher = "Morgan Kaufmann Publishers",

   volume = "22",

   pages = "215-287",

   issn = "1076-9757",

   year = "2004"

}