@misc{indiciae58dd6678da61,
  title = {Ecological bias, confounding, and effect modification.},
  author = {S Greenland and H Morgenstern},
  year = {1989},
  doi = {10.1093/ije/18.1.269},
  url = {https://pubmed.ncbi.nlm.nih.gov/2656561/},
  note = {Source identifier: 2656561}
}