@misc{indiciae723fcce00111,
  title = {Statistics notebook: entry II.B: Observational study, (1) retrospective study, and (2) prospective study.},
  author = {P N de Land and W W Chase},
  year = {1991},
  doi = {10.1097/00006324-199102000-00012},
  url = {https://pubmed.ncbi.nlm.nih.gov/2027656/},
  note = {Source identifier: 2027656}
}