@article{anoteonthecomplexityofthecausal,
  title = {A note on the complexity of the causal ordering problem},
  author = {Bernardo Gonçalves and Fabio Porto},
  year = {2015},
  eprint = {1508.05804},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1508.05804v2},
}