TY  - RPRT
TI  - Randomization by cluster. Sample size requirements and analysis.
AU  - A Donner
AU  - N Birkett
AU  - C Buck
PY  - 1981
DO  - 10.1093/oxfordjournals.aje.a113261
UR  - https://pubmed.ncbi.nlm.nih.gov/7315838/
ID  - 7315838
ER  -