TY  - RPRT
TI  - Classification schemes for epidemiologic research designs.
AU  - S Greenland
AU  - H Morgenstern
PY  - 1988
DO  - 10.1016/0895-4356(88)90155-2
UR  - https://pubmed.ncbi.nlm.nih.gov/3418359/
ID  - 3418359
ER  -