TY  - RPRT
TI  - The four functions: a conceptual analysis.
AU  - I N Marshall
PY  - 1968
DO  - 10.1111/j.1465-5922.1968.00001.x
UR  - https://pubmed.ncbi.nlm.nih.gov/4866953/
ID  - 4866953
ER  -