TY  - RPRT
TI  - Ecologic studies in epidemiology: concepts, principles, and methods.
AU  - H Morgenstern
PY  - 1995
DO  - 10.1146/annurev.pu.16.050195.000425
UR  - https://pubmed.ncbi.nlm.nih.gov/7639884/
ID  - 7639884
ER  -