TY  - RPRT
TI  - Randomised controlled trials: sampling.
AU  - P C Elwood
PY  - 1982
DO  - 10.1111/j.1365-2125.1982.tb01429.x
UR  - https://pubmed.ncbi.nlm.nih.gov/7082529/
ID  - 7082529
ER  -