TY  - RPRT
TI  - Identifiability and exchangeability for direct and indirect effects.
AU  - J M Robins
AU  - S Greenland
PY  - 1992
DO  - 10.1097/00001648-199203000-00013
UR  - https://pubmed.ncbi.nlm.nih.gov/1576220/
ID  - 1576220
ER  -