TY  - RPRT
TI  - Observational epidemiological studies: values and limitations.
AU  - François Gueyffier
PY  - 2003
DO  - 10.1097/00004872-200304000-00004
UR  - https://pubmed.ncbi.nlm.nih.gov/12658007/
ID  - 12658007
ER  -