TY  - RPRT
TI  - Causality inference in observational vs. experimental studies. An empirical comparison.
AU  - K Gray-Donald
AU  - M S Kramer
PY  - 1988
DO  - 10.1093/oxfordjournals.aje.a114891
UR  - https://pubmed.ncbi.nlm.nih.gov/3282432/
ID  - 3282432
ER  -