@misc{indiciaed94848f31e9c,
  title = {Randomization by cluster. Sample size requirements and analysis.},
  author = {A Donner and N Birkett and C Buck},
  year = {1981},
  doi = {10.1093/oxfordjournals.aje.a113261},
  url = {https://pubmed.ncbi.nlm.nih.gov/7315838/},
  note = {Source identifier: 7315838}
}