TY  - RPRT
TI  - AN ELECTIVE-PERIOD EXPERIMENT.
AU  - A G WATKINS
PY  - 1964
DO  - 10.1016/s0140-6736(64)90644-0
UR  - https://pubmed.ncbi.nlm.nih.gov/14172367/
ID  - 14172367
ER  -