@article{HagueOng2008,
  author = "M. Hague and C.-H. L. Ong",
  doi = "10.2168/LMCS-4(4:14)2008",
  journal = "Logical Methods in Computer Science",
  title = "Symbolic Backwards-Reachability Analysis for Higher-Order Pushdown Systems",
  url = "http://www.lmcs-online.org/ojs/viewarticle.php?id=363&layout=abstract",
  volume = "4",
  year = "2008",
}