TY  - RPRT
TI  - Matching and efficiency in cohort studies.
AU  - S Greenland
AU  - H Morgenstern
PY  - 1990
DO  - 10.1093/oxfordjournals.aje.a115469
UR  - https://pubmed.ncbi.nlm.nih.gov/2293747/
ID  - 2293747
ER  -