@misc{indiciaea53104ec568a,
  title = {Graphical models for causation, and the identification problem.},
  author = {David A Freedman},
  year = {2004},
  doi = {10.1177/0193841x04266432},
  url = {https://pubmed.ncbi.nlm.nih.gov/15245621/},
  note = {Source identifier: 15245621}
}