@misc{indiciaedbd67ca83c21,
  title = {Design versus directionality.},
  author = {S Greenland and H Morgenstern},
  year = {1991},
  doi = {10.1016/0895-4356(91)90269-f},
  url = {https://pubmed.ncbi.nlm.nih.gov/1995777/},
  note = {Source identifier: 1995777}
}