@inproceedings{HMO11,
  title = "A Fragment of ML Decidable by Visibly Pushdown Automata",
  author = "David Hopkins and Andrzej S. Murawski and C.-H. Luke Ong",
  year = "2011",
  booktitle = "ICALP ",
  pages = "149-161",
}
@article{hopkins09,
  title = "Homer: A Higher-order Observational equivalence Model checkER",
  author = "David Hopkins and Luke Ong",
  year = "2009",
  journal = "CAV 09",
}