@misc{indiciaec10c91617971,
  title = {The control of confounding by intermediate variables.},
  author = {J Robins},
  year = {1989},
  doi = {10.1002/sim.4780080608},
  url = {https://pubmed.ncbi.nlm.nih.gov/2749074/},
  note = {Source identifier: 2749074}
}