Further reading
Information about SAS names, and rules for naming elements in SAS – available here: https://v8doc.sas.com/sashtml/lgref/z1031056.htm.
Charlson Comorbidity Index – more information is available here: https://healthcaredelivery.cancer.gov/seermedicare/considerations/comorbidity.html.
PROC DATASETS
tip sheet from SAS – available here: https://support.sas.com/rnd/base/Tipsheet_DATASETS.pdf.