TY  - RPRT
TI  - Observational studies identify associations, not causality.
AU  - Arnold J Berry
PY  - 2005
DO  - 10.1213/01.ane.0000173754.86959.9d
UR  - https://pubmed.ncbi.nlm.nih.gov/16192554/
ID  - 16192554
ER  -