@misc{indiciaeb6f5b91b7090,
  title = {Observational study of behavior: sampling methods.},
  author = {J Altmann},
  year = {1974},
  doi = {10.1163/156853974x00534},
  url = {https://pubmed.ncbi.nlm.nih.gov/4597405/},
  note = {Source identifier: 4597405}
}