@misc{indiciae8a9cb7711697,
  title = {Study design VI - Ecological studies.},
  author = {Kate Ann Levin},
  year = {2006},
  doi = {10.1038/sj.ebd.6400454},
  url = {https://pubmed.ncbi.nlm.nih.gov/17187048/},
  note = {Source identifier: 17187048}
}