TY  - RPRT
TI  - Prevalence, incidence and duration.
AU  - J Freeman
AU  - G B Hutchison
PY  - 1980
DO  - 10.1093/oxfordjournals.aje.a113043
UR  - https://pubmed.ncbi.nlm.nih.gov/6969024/
ID  - 6969024
ER  -