TY  - RPRT
TI  - Methodologic issues in observational studies.
AU  - Arthur Hartz
AU  - J L Marsh
PY  - 2003
DO  - 10.1097/01.blo.0000079325.41006.95
UR  - https://pubmed.ncbi.nlm.nih.gov/12897594/
ID  - 12897594
ER  -