TY  - RPRT
TI  - Invited commentary: ecologic studies--biases, misconceptions, and counterexamples.
AU  - S Greenland
AU  - J Robins
PY  - 1994
DO  - 10.1093/oxfordjournals.aje.a117069
UR  - https://pubmed.ncbi.nlm.nih.gov/8178788/
ID  - 8178788
ER  -